Etch selectivity control in atomic layer etching

ABSTRACT

Apparatuses and methods are provided. Some methods may include providing a substrate to a processing chamber, the substrate having a first material adjacent to and covering a surface of a second material, modifying a layer of the first material by flowing a first process gas onto the substrate and thereby creating a modified layer of the first material, removing the modified layer of the first material by flowing a second process gas onto the substrate, and converting, when the surface of the second material is uncovered via removal of the modified layer, the surface to a converted layer of the second material by flowing a third process gas onto the substrate, in which the first and second process gases are less reactive with the converted layer than with the first material and the second material.

RELATED APPLICATIONS

A PCT request form is filed concurrently with this specification as partof the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed PCT request form is incorporated by reference hereinin its entirety and for all purposes.

BACKGROUND

Semiconductor fabrication often involves patterning schemes and otherprocesses whereby some materials are selectively etched to preventetching of other exposed surfaces of a substrate. As device geometriesbecome smaller and smaller, high etch selectivity processes aredesirable to achieve effective etching of desired materials withoutetching of other materials.

The background description provided herein is for the purposes ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein. Included among these aspects areat least the following implementations, although further implementationsmay be set forth in the detailed description or may be evident from thediscussion provided herein.

In some embodiments, a method may be provided. The method may includeproviding a substrate to a processing chamber, the substrate having afirst material adjacent to and covering a surface of a second material,modifying a layer of the first material by flowing a first process gasonto the substrate and thereby creating a modified layer of the firstmaterial, removing the modified layer of the first material by flowing asecond process gas onto the substrate, and converting, when the surfaceof the second material is uncovered via removal of the modified layer,the surface to a converted layer of the second material by flowing athird process gas onto the substrate, in which the first and secondprocess gases are less reactive with the converted layer than with thefirst material and the second material.

In some embodiments, the method may further include modifying, after theconverting, the converted layer to a modified converted layer ofmaterial by flowing a fourth process gas onto the substrate, andremoving the modified converted layer by flowing a fifth process gasonto the substrate.

In some embodiments, flowing the third process gas may occur before themodifying.

In some embodiments, flowing the third process gas may occur after themodifying.

In some such embodiments, flowing the third process gas may occur beforethe removing.

In some further such embodiments, the method may further include flowinga purge gas after flowing the third process gas and before the removing.

In some such embodiments, flowing the third process gas may occur afterthe removing.

In some embodiments, flowing the third process gas onto the substratemay at least partially overlap with flowing the first process gas ontothe substrate.

In some embodiments, flowing the third process gas onto the substratemay at least partially overlap with flowing the second process gas ontothe substrate.

In some embodiments, flowing the third process gas onto the substratemay at least partially overlap with flowing the first process gas ontothe substrate and with flowing the second process gas onto thesubstrate.

In some embodiments, the converting may occur when the surface of thesecond material is uncovered during or after the removing of the firstmaterial.

In some embodiments, during the removing, the second process gas mayremove the modified layer of the first material at a first etch rate,during the removing, the second process gas may remove the convertedlayer at a second etch rate that is about equal to or less than 50% ofthe first etch rate.

In some such embodiments, the second etch rate may be about equal to orless than 15% of the first etch rate.

In some such embodiments, during the removing, the second process gasmay be capable of removing the second material at a third etch ratehigher than the first etch rate.

In some embodiments, the first process gas may include modifyingmolecules, the second process gas may include removal molecules, and thethird process gas may include converting molecules.

In some embodiments, the third process gas may include a precursor.

In some embodiments, the converted layer may be a monoatomic layer ofthe second material.

In some embodiments, the first material and the second material may beoxides.

In some embodiments, the first material and/or the second material maybe semiconductor oxides.

In some embodiments, the converted layer may be passive to the secondprocess gas.

In some embodiments, a reaction between the converted layer and thesecond process gas may not produce byproducts.

In some embodiments, the method may further include repeating themodifying and the removing to remove an amount the first material beforethe converting.

In some embodiments, the first material may include an aluminum oxide,the second material may include a zinc oxide, the first process gas mayinclude a hydrogen fluoride, the second process gas may includetrimethylaluminum, the third process gas may include zirconiumtetrachloride, and the converted layer may include a zirconium oxide.

In some embodiments, the method may further include removing theconverted layer by flowing a fourth process gas onto the substrate, inwhich the fourth process gas comprises dimethylaluminum chloride.

In some embodiments, the converting may include a cation exchangebetween an element in the third process gas and the second material.

In some embodiments, the modifying and the removing may occur while thesubstrate is maintained at the same, or substantially the same,temperature.

In some embodiments, the modifying may occur while the substrate ismaintained at a first temperature, and the removing may occur while thesubstrate is maintained at a second temperature different than the firsttemperature.

In some embodiments, during the converting, water vapor may not beprovided to the substrate.

In some embodiments, a method may be provided. The method may includeproviding a substrate to a processing chamber, the substrate having afirst material adjacent to and covering a surface of a second material,modifying a layer of the first material by flowing a first process gasonto the substrate and thereby creating a modified layer of the firstmaterial, removing the modified layer of the first material by flowing asecond process gas onto the substrate, and selectively converting, whenthe surface of the second material is uncovered via removal of themodified layer, the surface of the second material to a layer of etchstop material, and the layer of etch stop material is only positioned ontop of the second material, such that during the removing, the modifiedlayer of the first material and the layer of etch stop material areexposed to the second process gas and the second process gas is lessreactive with the layer of etch stop material than with the modifiedlayer of the first material and the second material.

In some embodiments, an apparatus for semiconductor processing may beprovided. The apparatus may include a processing chamber that includesan interior and a substrate support configured to support a substrate inthe interior, a process gas unit configured to flow a first process gascomprising a modifying molecule onto the substrate in the processingchamber, a second process gas comprising a removal molecule onto thesubstrate in the processing chamber, and a third process gas comprisinga conversion molecule onto the substrate in the processing chamber, anda controller with instructions that are configured to cause the firstprocess gas to flow onto the substrate and thereby create a modifiedlayer of a first material on the substrate, in which the substrate hasthe first material adjacent to and covering a surface of a secondmaterial, cause the second process gas to flow onto the substrate andthereby remove the modified layer of the first material, and cause thethird process gas to flow onto the substrate to convert, when thesurface of the second material is uncovered, the surface to a convertedlayer of the second material, in which the first and second processgases are less reactive with the converted layer than with the firstmaterial and the second material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example process flow diagram for performing operationsin accordance with disclosed embodiments.

FIG. 2 depicts an example schematic illustration of atomic layer etchingin accordance with disclosed embodiments.

FIG. 3 depicts another example process flow diagram for performingoperations in accordance with disclosed embodiments.

FIG. 4A depicts yet another example process flow diagram for performingoperations in accordance with disclosed embodiments.

FIG. 4B depicts another example process flow diagram for performingoperations in accordance with disclosed embodiments.

FIG. 5 depicts another example process flow diagram for performingoperations in accordance with disclosed embodiments.

FIGS. 6A through 6D further illustrate various flows of the thirdprocess gas onto the wafer.

FIG. 7 depicts an example apparatus for semiconductor processing inaccordance with disclosed embodiments, including thermal atomic layeretching.

FIGS. 8A-8C illustrate an embodiment of an adjustable gap capacitivelycoupled confined RF plasma reactor that may be used for performing theetching operations described herein.

FIG. 9 depicts a semiconductor process cluster architecture with variousmodules that interface with a vacuum transfer module.

FIG. 10 depicts a schematic view of a process station that may be usedto deposit material.

FIG. 11 depicts a schematic view of a multi-station processing tool.

FIG. 12 depicts a block diagram of a processing system suitable forconducting thin film deposition processes in accordance with certainembodiments.

FIG. 13 depicts a schematic view of a multi-station processing tool.

FIG. 14 depicts another schematic view of a multi-station processingtool.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the presented embodiments. Thedisclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments will be described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

In this application, the terms “semiconductor wafer,” “wafer,”“substrate,” “wafer substrate,” and “partially fabricated integratedcircuit” are used interchangeably. One of ordinary skill in the artwould understand that the term “partially fabricated integrated circuit”can refer to a silicon wafer during any of many stages of integratedcircuit fabrication thereon. A wafer or substrate used in thesemiconductor device industry typically has a diameter of 200 mm, or 300mm, or 450 mm. The following detailed description assumes the inventionis implemented on a wafer. However, the invention is not so limited. Thework piece may be of various shapes, sizes, and materials. In additionto semiconductor wafers, other work pieces that may take advantage ofthis invention include various articles such as printed circuit boards,magnetic recording media, magnetic recording sensors, mirrors, opticalelements, micro-mechanical devices and the like.

Introduction and Context

Semiconductor fabrication processes often involve patterning and etchingof various materials, including conductors, semiconductors, anddielectrics. Some examples include conductors, such as metals or carbon;semiconductors, such as silicon or germanium; and dielectrics, such assilicon oxide, aluminum oxide, zirconium dioxide, hafnium dioxide,silicon nitride, and titanium nitride. Atomic layer etching (“ALE”)processes remove thin layers of material using sequential self-limitingreactions. Generally, an ALE cycle is the minimum set of operations usedto perform an etch process one time, such as etching a monolayer. Theresult of one ALE cycle is that at least some of a film layer on asubstrate surface is etched. Typically, an ALE cycle includes amodification operation to form a reactive layer, followed by a removaloperation to remove or etch only this reactive layer. The cycle mayinclude certain ancillary operations such as removing one of thereactants or byproducts, as well as a cleaning operation to removeresidues that have built up on surfaces of the processing chamber.Generally, a cycle contains one instance of a unique sequence ofoperations.

As an example, an ALE cycle may include the following operations: (i)delivery of a first process gas that is a reactant gas, (ii) purging ofthe reactant gas from the chamber, (iii) delivery of a second processgas that is a removal gas and an optional plasma, and (iv) purging ofthe chamber. In some embodiments, etching may be performednonconformally. In some instances, a cleaning operation may be performedafter one or more cycles to remove residues that have built up onsurfaces of the processing chamber. The modification operation generallyforms a thin, reactive surface layer with a thickness less than theun-modified material, such as one, two, or three, atomic layers thick,for instance, or less than a whole atomic layer in one cycle.

Some implementations of the ALE processes described herein may rely uponchemical reactions in conjunction maintaining the substrate at aparticular temperature or temperature range to drive chemical reactionsin the modification and/or the removal operations which may beconsidered “thermal ALE”. In some embodiments, this thermal ALE may beconsidered an isotropic etch. In some embodiments, one or more layers ofthe substrate may be modified with chemical adsorption (hereinafter“chemisorption”), not with a plasma, while the substrate is maintainedat a first temperature, after which the one or more modified layers ofthe substrate may be removed with desorption, not with a plasma, whilethe substrate is at a second temperature. In some embodiments, the firstand second temperatures may be the same, while in some other embodimentsthey may be different than each other. Chemisorption and desorption aretemperature dependent chemical reactions that may occur in separatetemperature regimes, may occur in partially overlapping temperatureregimes, or may occur in the same temperature regime. Because of this,some of the thermal ALE techniques described herein maintain thetemperature of the substrate at the same, or substantially the same,temperature during the modification and removal operations. Some otherembodiments modulate the temperature of the substrate between themodification and removal operations in order to enable and utilizechemisorption that occurs at one temperature for the modificationoperation, and to enable and utilize desorption that occurs at adifferent temperature for the removal operation.

In some embodiments of thermal ALE, a plasma may be used during themodification operation and not during the removal operation, while insome other embodiments, a plasma may be used during both themodification and removal operations, along with varying temperaturesduring these operations.

In some thermal ALE processes, one or more surface layers of materialare modified by chemisorption while the substrate is maintained at afirst temperature; this may result in the creation of one or moremodified surface layers of the substrate. The substrate includes layersof material and exposed surfaces that may be a uniform layer of materialor may be a non-uniform layer that includes different molecules andelements. A first process gas with modifying molecules may be flowedonto the substrate that is maintained at the first temperature. In someembodiments, the modifying molecules may include a halogen, such asfluorine, in order to halogenate exposed molecules on the substrate,while some embodiments may include oxygen in order to oxidize exposedmolecules on the substrate. The first process gas may also include acarrier gas, such as N₂, Ar, He, and Ne. This first temperature allowsfor chemisorption between the modifying molecules and at least some ofthe molecules in the exposed surface(s) of material.

Although the term “first temperature” is used, the temperaturesdiscussed herein may be considered both a specific temperature, or maybe a temperature range like highlighted in FIGS. 2 and 3 . In someembodiments, the first temperature may be between about 20° C. and 500°C., about 20° C. and 150° C., about 20° C. and 100° C., about 20° C. and80° C., about 200° C. and 600° C., about 200° C. and 500° C., about 200°C. and 350° C., or about 350° C. and 500° C., for example. Additionally,the substrate may be maintained at the temperature during all, orsubstantially all (e.g., at least 80%, 90%, or 95%), of the modificationoperation. The duration of the modification operation may be theduration for which modification of substantially all (e.g., at least80%, 90%, or 95%) of desired exposed molecules on the substrate occurs.This may range from about 0.5 seconds to about 10 seconds, 0.5 secondsto about 5 seconds, about 1 second to about 5 seconds, or about 30seconds to two minutes, for example.

After the modification operation, an optional purge operation may beperformed. In some of the embodiments in which the modification andremoval operations are performed at different temperatures, after themodification operation, the temperature of the substrate may be broughtto a second temperature, and an optional purge operation may beperformed. This second temperature may be the temperature at whichdesorption occurs for the one or more modified surface layers. In someembodiments, the second temperature may be greater than the firsttemperature and the temperature of substrate may be raised from thefirst temperature to the second temperature. In some other embodiments,the second temperature may be less than the first temperature, and inthese embodiments, the temperature of the substrate may be activelycooled from the first temperature to the second temperature. Thesubstrate may be heated using radiant heating, convection heating,solid-to-solid heat transfer, or with a plasma. Additionally, thesubstrate top, bottom, or both, may be heated. The heating of thesubstrate may also occur in a non-linear fashion, in some embodiments,and the substrate may be actively cooled in various manners. As notedabove, in some embodiments, the second temperature may be the same, orsubstantially the same, as the first temperature such that themodification and removal operations are performed at the same, orsubstantially the same, temperature.

The one or more modified surface layers may be removed while thesubstrate is maintained at the second temperature. In some embodiments,the second temperature alone may enable and cause desorption of themodified molecules from the substrate thereby removing the modifiedmolecules from the substrate. In some other embodiments, a secondprocess gas with removal molecules may be flowed onto the substrate,including onto the exposed surfaces of the substrate. The second processgas may also include a carrier gas as described above. These removalmolecules may react with the modified molecules to form a differentvolatile molecule, which may be considered a volatized molecule. Thisvolatized molecule may in turn be removed from the substrate bydesorption when the substrate is at the second temperature. In someembodiments, this flowing of the second process gas may be part of theremoval operation or may be a separate operation that occurs before,after, or during the heating of the substrate.

In some embodiments, the second temperature may be the same or differentthan the first temperature, and may range between about 20° C. and 500°C., about 20° C. and 150° C., about 20° C. and 100° C., about 20° C. and80° C., about 200° C. and 600° C., about 200° C. and 500° C., about 200°C. and 350° C., or about 350° C. and 500° C., for example. Additionally,the substrate may be maintained at the temperature during all, orsubstantially all (e.g., at least 80%, 90%, or 95%), of the removaloperation. The duration of the removal operation may be the duration forwhich desorption of substantially all (e.g., at least 80%, 90%, or 95%)of desired molecules on the substrate occurs. This may range from about0.5 seconds to about 10 seconds, about 0.5 seconds to about 5 seconds,about 1 second to about 5 seconds, about 0.5 seconds to two minutes, orabout 30 seconds and two minutes.

In some other ALE processes, ionic energy, such as from a plasma, may beused to drive the modification and/or the removal operations. In anexample modification operation, a substrate may be chlorinated byintroducing chlorine into the chamber. Chlorine is used as an exampleetchant species or etching gas, but it will be understood that adifferent etching gas may be introduced into the chamber. The etchinggas may be selected depending on the type and chemistry of the substrateto be etched. A plasma may be ignited and chlorine reacts with thesubstrate for the etching process; the chlorine may react with thesubstrate or may be adsorbed onto the surface of the substrate. Thespecies generated from a plasma can be generated directly by forming aplasma in the process chamber housing the substrate or they can begenerated remotely in a process chamber that does not house thesubstrate, and can be supplied into the process chamber housing thesubstrate.

In some instances, a purge may be performed after any of the operationsdescribed herein, including after the modification and/or removaloperations. In a purge operation, non-surface-bound active modifyingmolecules, such as a chlorine or halogen species, may be removed fromthe process chamber. This can be done by purging and/or evacuating theprocess chamber to remove the active species, without removing theadsorbed layer. In some implementations that use a plasma, the speciesgenerated in a plasma can be removed by stopping the plasma and allowingthe remaining species to decay, optionally combined with purging and/orevacuation of the chamber. Purging can be done using any inert gas suchas N2, Ar, Ne, He and their combinations.

In a removal operation utilizing a plasma, the substrate may be exposedto an energy source to etch the substrate by directional sputtering(this may include activating or sputtering gas or chemically reactivespecies that induce removal). In some embodiments, the removal operationmay be performed by ion bombardment using argon or helium ions. Duringremoval, a bias may be optionally turned on to facilitate directionalsputtering. In some embodiments, ALE may be isotropic; in some otherembodiments ALE is not isotropic when directional ions are used in theremoval process.

In various examples, the modification and removal operations of thermalALE and plasma-assisted ALE may be repeated in cycles, such as about 1to about 30 cycles, or about 1 to about 20 cycles. Any suitable numberof ALE cycles may be included to etch a desired amount of film. In someembodiments, ALE is performed in cycles to etch about 1 Angstroms (Å) toabout 50 Å of the surface of the layers on the substrate. In someembodiments, cycles of ALE etch between about 2 Å and about 50 Å of thesurface of the layers on the substrate. In some embodiments, each ALEcycle may etch at least about 0.1 Å, 0.5 Å, 1 Å, 2 Å, or 3 Å.

In some instances, prior to etching, the substrate may include a blanketlayer of material, such as silicon or germanium. The substrate mayinclude a patterned mask layer previously deposited and patterned on thesubstrate. For example, a mask layer may be deposited and patterned on asubstrate including a blanket amorphous silicon layer. The layers on thesubstrate may also be patterned. Substrates may have “features” such asvia or contact holes, which may be characterized by one or more ofnarrow and/or re-entrant openings, constrictions within the feature, andhigh aspect ratios. One example of a feature is a hole or via in asemiconductor substrate or a layer on the substrate. Another example isa trench in a substrate or layer. In various instances, the feature mayhave an under-layer, such as a barrier layer or adhesion layer.Non-limiting examples of under-layers include dielectric layers andconducting layers, e.g., silicon oxides, silicon nitrides, siliconcarbides, metal oxides, metal nitrides, metal carbides, and metallayers. Another example feature may include overhangs or shelves thatmay require an etch in a location that may not be accessible withdirectional ions.

In some thermal ALE and/or plasma-assisted ALE processes, it isdesirable to etch a target material without etching another materialcovered by the target material, sometimes described as etching thetarget material with selectivity to the other material. With somematerials and etching chemistries, typical ALE processing and chemistrycannot achieve this selectivity. In some of these typical ALE processes,when the etch front removes the target material and reaches theunderlying other material, it may undesirably continue etching andremoving that other material. This undesirable etching may occur whenetching, for example, high-k dielectrics, high-k oxides, semiconductors,metals, or other oxides that are covering other high-k dielectrics,high-k oxides, semiconductors, metals. Some of these conventional ALEprocesses therefore do not have the ability to remove one high-k oxidewith selectivity to another high-k oxide or to a semiconductor.

Etching Techniques with High Selectivity

Provided herein are techniques and apparatuses for increasing etchselectivity between materials. This includes etching one material,referred to as the target material, that covers another material andreducing and/or limiting the etching of this other material. Someembodiments may include introducing a third process gas that creates anetch stop layer which prevents and/or reduces the etching of theunderlying material. This third process gas may also cause limited to noetching of the target material. In some embodiments, the third processgas may be considered both a gas in which substantially all (e.g., atleast 99% or more) of its constituents are in the gas phase, as well asa vapor in which its constituents may be in both the gas phase andliquid phase as suspended droplets. In some implementations, the etchstop layer may be a deposited layer of material that is selectivelydeposited onto the underlying material. The etch stop layer, whether aconverted layer or a deposited layer, may be considered less reactivewith the etching chemistry than the second layer of material and themodified layer of material which limits and reduces the etching of thisetch stop material relative to the second layer of material and themodified layer of material.

In some implementations, the etch stop layer may be created byconverting an exposed surface of the underlying material to a convertedlayer that is capable of withstanding the etching chemistry used toremove the target material. This etch stop layer, or converted layer, isformed by a conversion of the layer of the underlying material which, insome instances, may be achieved by a cation exchange between the thirdprocess gas and the underlying material without altering the compositionof the target material or interfering with the primary etch chemistryused to etch the target material. This may be a conversion of at leastone monoatomic layer of that material. In some implementations, the etchstop layer is formed via conversion of the surface of the underlyingmaterial, when the surface is exposed, using vaporous compounds. Thethird process supplies a cationic constituent in the vapor phase forthis conversion; the remaining elements of this conversion are providedby the surface of the underlying material. In some embodiments, thecationic constituents of the underlying material are converted tovolatile molecules that leave the surface of, or desorb from, thesubstrate. The cation in the third process gas, e.g., the incomingvapor, exchanges its ligands (e.g., a chlorine) with the ligand on thesurface (e.g., oxygen), and thereby becomes solid or nonvolatile.

Additionally, it is desirable in some implementations to have theetching chemistry, the third process gas, and the resulting etch stoplayer be compatible with each other so that, for example, the etching ofthe first material can continue while the conversion layer is beingformed and protecting the underlying layer of material, and/or so thatthe etching chemistry does not react with the third process gas or etchthe etch stop layer. For example, the first material may not be etchedat the same time and/or rate at various locations on and/or across thewhole wafer. For various reasons, some etching processes begin at thecenter of a wafer and continue radially outwards thereby etching acenter region before an edge region. This may cause the removal of thedesired amount of material in the center region faster than in the edgeregion, which may require the etching chemistry to continue flowing ontothe wafer after the desired material has been removed from some parts ofthe wafer.

In another example, the first material may be deposited on the sides andbottom of a hole (or via, or trench), and may cover the second materialthat is also in the hole, and because etch rates of horizontal surfacesare sometimes less than etch rates of vertical surfaces, the bottomand/or top of the hole of the hole, via, or trench may be etched toexpose the second material before the first material is removed on thesides of the hole. This may require continuing the etching within thehole to remove the first material on the sides of the hole while thesecond material is exposed at the bottom and/or top of the hole. It istherefore desirable in some implementations to form the conversion layeron the wafer where the etching has exposed the underlying material whilesimultaneously allowing the etching of the first material to continue onthe wafer. Accordingly, some implementations provided herein useconversion molecules and etching chemistry that do not adversely affectone another so that the etching of the first material can continue onthe wafer while the conversion layer is also formed when the underlyingmaterial is exposed by that etching.

The chemistry used to etch the target material may etch the etch stoplayer at an etch rate less the etch rate of the target material and/orthe other material, such as less than or equal to 50%, 25%, 15%, 10%,5%, 1%, 0.1%, or 0.05% of the etch rate of the target material and/orthe other material.

As discussed in more detail below, the third process gas may beintroduced during various aspects of the processing. This may includeco-flowing the third process gas during one or more ALE cycles, duringan ALE process step such as the modifying or the removing, and/orflowing the third process gas while other process gases are not flowed,such as in-between removing and modifying operations. An example processmay include performing the modification operation, followed by a purge,followed by flowing the third process gas, followed by another purge,and then followed by the removal operation. Optionally, the conversionlayer may be removed by a separate modification operation with adifferent modifying molecule and a separate removal operation with adifferent removal molecule.

FIG. 1 depicts an example process flow diagram for performing operationsin accordance with disclosed embodiments. In block 101, a wafer isprovided to a processing chamber configured to performing etching of thewafer. The wafer may have at least two materials deposited thereon, witha first material adjacent to and covering a surface of a secondmaterial. This covering may be a vertical covering such that when thewafer is positioned on its bottom surface, the first and secondmaterials are vertically arranged with the first material above andcovering the second material. This covering may alternatively oradditionally be a horizontal covering such that when the wafer ispositioned on its bottom surface, the first and second materials arehorizontally arranged with respect to each other with the first materialcovering the second material. In some embodiments, both the covering maybe both vertical and horizonal coverings. As mentioned above, this mayinclude the first material covering the second material along thesidewalls of a hole, via, or trench which poses an additional challengebecause etch rates on horizontal surfaces may exceed those on verticalsurfaces. In one single hole or via, etching of the vertical surfacemust continue while the conversion layer is formed and forming on thehorizontal surface.

In block 103, a modification operation of the first material, alsoconsidered the target material, may be performed. The modificationoperation may include flowing a first process gas comprising a modifyingmolecule onto the wafer to form a thin, reactive surface layer that ismore easily removed than the un-modified material in the subsequentremoval operation. These modifying molecules may include, for example,halogen species such as chlorine or fluorine. Fluorine is used as anexample etchant species in disclosed embodiments, and it may be flowedonto the substrate as hydrogen fluoride (HF), but it will be understoodthat in some embodiments, a different etching gas is introduced into thechamber. The etching gas may be selected depending on the type andchemistry of the substrate to be etched.

In some embodiments, an activation energy may be provided to assist withovercoming the activation barrier for the modifying molecule to adsorbon the semiconductor. This activation energy may be provided withthermal energy, radical energy, or both, which may include heating thesubstrate and/or generating a plasma or photons. This adsorption of themodifying molecule onto the first material may be considered chemicaladsorption or “chemisorption” which is an energy dependent (e.g., atemperature dependent) chemical reaction. For some thermal ALEtechniques, this chemisorption during the modification operation mayonly occur at a particular temperature range that enables the activationbarrier of the molecules in the layer of material and the incomingmodifying molecules to be overcome which allows for dissociation andchemical bonding between these molecules and an adsorbate in themodifying molecule. Outside of this temperature range, the chemisorptionmay not occur, or may occur at undesirable (e.g., slow) rates.

Accordingly, some implementations of block 103 include one or moresurface layers of material are modified by chemisorption while thesubstrate is maintained at a first temperature; this may result in thecreation of one or more modified surface layers of the substrate. Thesubstrate includes layers of material and exposed surfaces that may be auniform layer of material or may be a non-uniform layer that includesdifferent molecules and elements. A first process gas with modifyingmolecules may be flowed onto the substrate that is maintained at thefirst temperature. In some embodiments, the modifying molecules mayinclude a halogen, such as fluorine, in order to halogenate exposedmolecules on the substrate, while some embodiments may include oxygen inorder to oxidize exposed molecules on the substrate. In variousembodiments, modifying molecules are introduced into the chamber in agaseous form or vapor form (e.g., including both gas liquid forms) andmay be optionally accompanied by a carrier gas such as nitrogen, argon,helium, or neon, for instance. This first temperature allows forchemisorption between the modifying molecules and at least some of themolecules in the exposed surface(s) of material.

Although the term “first temperature” is used, the temperaturesdiscussed herein may be considered both a specific temperature, or maybe a temperature range like highlighted in FIGS. 2 and 3 . In someembodiments, the first temperature may be between about 20° C. and 500°C., about 20° C. and 150° C., about 20° C. and 100° C., about 20° C. and80° C., about 200° C. and 600° C., about 200° C. and 500° C., about 200°C. and 350° C., or about 350° C. and 500° C., for example. Additionally,the substrate may be maintained at the temperature during all, orsubstantially all (e.g., at least 80%, 90%, or 95%), of the modificationoperation. The duration of the modification operation may be theduration for which modification of substantially all (e.g., at least80%, 90%, or 95%) of desired exposed molecules on the substrate occurs.This may range from about 0.5 seconds to about 10 seconds, 0.5 secondsto about 5 seconds, or about 1 second to about 5 seconds, for example.

In some implementations that utilize plasma-assisted modification, thespecies generated from a plasma, for instance, can be generated directlyby forming a plasma in the process chamber housing the substrate or theycan be generated remotely in a process chamber that does not house thesubstrate, and can be supplied into the process chamber housing thesubstrate.

Although not shown in FIG. 1 , an optional purge operation may beperformed after block 103. In a purge operation, non-surface-boundactive modifying molecules, such as the fluorine or chlorine species,may be removed from the process chamber, the chamber walls, the chambergas volume, and/or the substrate. This can be done by purging and/orevacuating the process chamber to remove the active species, withoutremoving the adsorbed layer. The species generated in a plasma can beremoved by stopping the plasma and allowing the remaining species todecay, optionally combined with purging and/or evacuation of thechamber. Purging can be done using any inert gas such as N₂, Ar, Ne, Heand their combinations.

In block 105, a removal operation of the modified layer of the firstmaterial is performed. This may include flowing a second process gascomprising removal molecules onto the substrate and exposing the waferto an energy source, such as thermal energy, a plasma, or activating orsputtering gas or chemically reactive species that induces removal, suchas argon or helium, to etch the substrate by directional sputtering. Forsome thermal ALE implementations, the removal operation may occur at thesame, or substantially the same temperature, as the removal operation(i.e., at the first temperature). In some other thermal ALEimplementations, the removal operation may occur at a second temperatureor temperature range different than the first temperature range of themodification operation of block 103.

For desorption, a particular temperature range enables the activationbarrier of the modified molecule to be overcome which allows for therelease of the modified layer from the surface of the substrate. In someexamples, the temperature ranges at which chemisorption and desorptionoccur do not overlap while in others they may partially or fullyoverlap. Accordingly, in order to remove a molecule from a substrateusing chemisorption and desorption, some implementations may maintainthe substrate at the same, or substantially same, temperature during theremoval and modification operations. In order to remove a molecule froma substrate using chemisorption and desorption that occur in differenttemperature regimes, the modification operation of block 103 may occurin the first temperature range and the removal operation of block 105may occur in the second different temperature range which may be higheror lower than the first temperature. Some such embodiments may performmultiple cycles to remove multiple layers of material by maintaining thesubstrate at the same, or substantially the same, temperature during theremoval and modification operations, while other embodiments mayrepeatedly heat and cool the substrate between the two temperatureregimes for chemisorption and desorption.

In some of the embodiments that use different temperature regimes,during or before block 105, the temperature of the substrate may bebrought to a second temperature that is different than the firsttemperature. In some other embodiments, the second temperature is thesame, or substantially the same, temperature as the first temperature.This second temperature may be the temperature at which desorptionoccurs for the one or more modified surface layers. In some embodiments,the second temperature may be greater than the first temperature, and inthese embodiments, block 105 may include heating the substrate from thefirst temperature to the second temperature. In some other embodiments,the second temperature may be less than the first temperature, and inthese embodiments, the substrate may be actively cooled from the firsttemperature to the second temperature. The substrate may be heated usingradiant heating, convection heating, solid-to-solid heat transfer, orwith a plasma. Additionally, the substrate top, bottom, or both, may beheated. The heating of the substrate may also occur in a non-linearfashion, in some embodiments, as discussed further below. As alsodescribed below, the substrate may be actively cooled in variousmanners.

In block 105, the one or more modified surface layers may be removedwhile the substrate is maintained at the second temperature. In someembodiments, the second temperature alone may enable and causedesorption of the modified molecules from the substrate thereby removingthe modified molecules from the substrate. In some other embodiments, asecond process gas with removal molecules may be flowed onto thesubstrate, including onto the exposed surfaces of the substrate. Thesecond process gas may also include a carrier gas as described above.These removal molecules may react with the modified molecules to form adifferent volatile molecule, e.g., a volatized molecule. This volatizedmolecule may in turn be removed from the substrate by desorption whenthe substrate is at the second temperature.

In some embodiments, the second temperature may be between about 20° C.and 500° C., about 20° C. and 150° C., about 20° C. and 100° C., about20° C. and 80° C., about 200° C. and 600° C., about 200° C. and 500° C.,about 200° C. and 350° C., or about 350° C. and 500° C., for example.Additionally, the substrate may be maintained at the temperature duringall, or substantially all (e.g., at least 80%, 90%, or 95%), of theremoval operation. The duration of the removal operation may be theduration for which desorption of substantially all (e.g., at least 80%,90%, or 95%) of desired molecules on the substrate occurs. This mayrange from about 0.5 seconds to about 10 seconds, about 0.5 seconds toabout 5 seconds, about 1 second to about 5, about 0.5 seconds to twominutes, or about 30 seconds to two minutes.

The performance of blocks 103 and 105 may be considered a single ALEcycle. In some implementations, these blocks 103 and 105 may be repeatedin order to perform multiple cycles and remove an atomic mono-layer aswell as multiple layers of the first material.

In block 107, the surface of the second material is converted to aconverted layer, i.e., an etch stop layer, that is capable ofwithstanding, or configured to withstand, the etching chemistry used toremove the first material. This conversion occurs when the surface ofthe second material is uncovered or exposed (e.g., via removal of thefirst material including removal of the modified layer of the firstmaterial), and in the presence of conversion molecules of a thirdprocess gas that has been, or is being flowed onto, the wafer. Thisconversion does not occur when the second material is still covered andnot exposed to the conversion molecules. In some implementations, theetch front must therefore remove the first material by modification andremoval as described above to reach and uncover the surface of thesecond material before, or when, the conversion of the second materialoccurs. Although block 107 is depicted after block 105, block 107 mayoccur concurrently with or after block 105. Additionally, as discussedin more detail below, the third process gas comprising conversionmolecules may be flowed onto the substrate in various ways, such asbefore and/or during the removal operation in block 105. In variousembodiments, the conversion molecules are introduced into the chamber ina vapor form or gaseous form and may be optionally accompanied by acarrier gas such as nitrogen, argon, helium, or neon, for instance.

FIG. 2 depicts an example schematic illustration of atomic layer etchingin accordance with disclosed embodiments. In diagrams 202 a-202 e asingle layer of material is etched from a wafer. In 202 a, the wafer isprovided and it has a first material illustrated with shaded circles andhaving two layers, and a second material, illustrated with whitecircles, adjacent to and covered by the first material, and having threelayers. Molecules of the first material are labeled as 204 and moleculesof the second material are labeled as 206, and the top layer of thefirst material may be considered a surface layer 208 of the firstmaterial. In 202 b, a first process gas with modifying molecules 210(the solid black circles, some of which are identified with identifier210) is introduced to the substrate which modifies the surface layer 208of the substrate. The schematic in 202 b shows that some of themodifying molecules 210 are adsorbed onto the molecules 204 of thesurface layer 208 of the substrate thereby creating modified surfacelayer 212 that includes modified molecules 214 (one modified molecule214 is identified inside a dotted ellipse in 202 b). For some thermalALE techniques, this diagram 202 b may occur while the substrate ismaintained at a first temperature as described above, e.g., that enableschemisorption of the modifying molecule on the surface of the firstmaterial. In some other implementations, this modification operation maybe plasma assisted. Although this Figure illustrates a single layerbeing modified, in some embodiments, multiple layers of the firstmaterial may be modified.

In 202 c, after the modified molecules 214 and the modified surfacelayer 212 have been created in 202 b, the first process gas may beoptionally purged from the chamber. In 202 d, removal molecules 216 areintroduced into the process chamber and in some embodiments, this mayoccur by flowing a second process gas comprising the removal molecules216, onto the substrate. In some thermal ALE embodiments, this removaloperation may be performed at a second temperature where desorption ofthe modified molecules 214 of the modified surface layer 212 from thesubstrate occurs; no plasma may be utilized in some of these removaloperations. In some embodiments, the second temperature is the same, orsubstantially the same, as the first temperature. In other embodiments,the first and second temperatures may be different than each other and,in these embodiments, the temperature may be changed from the firsttemperature to the second temperature by either heating or cooling thesubstrate. In some other embodiments, the second process gas may beintroduced with a plasma or a directional plasma, and ion bombardmentmay be performed to remove the modified surface of the substrate. Duringplasma-assisted operations, a bias may be applied to the substrate toattract ions toward it. Although this Figure illustrates a single layerbeing removed, in some embodiments multiple layers of the first materialmay be removed if they were previously modified. In 202 e, the modifiedmolecules 214, and therefore the modified surface layer 212, have beenremoved from the substrate and the second layer 218 of the firstmaterial remains covering the second material. In the example depictedin 202 e, the modifying molecules 210 are not present, but in someembodiments, these modifying molecules 210 may be present as shown, forexample, in 202 b. In some such embodiments, these modifying molecules210 may be introduced in subsequent process steps, such as in diagrams202 f and 202 g.

Diagrams 202 f and 202 g illustrate the wafer during and/or after aremoval operation, and illustrate an example conversion of the surfaceof the second material. During the operations of diagrams 202 a-202 e,the second material remains covered by the first material; the surfaceof the second material is not exposed in these operations. In diagram202 f, the removal molecules 216 have removed, or etched, some of thefirst material, i.e., some of the modified layer 218 of the firstmaterial, from covering the second material 206, thereby exposing thesurface of the second material, i.e., uncovering this surface viaremoval of the modified layer 218 of the first material. This exposedsurface of the second material 206 is illustrated in diagram 202 f withthree molecules of the second material 206 inside the dotted rectangle220. With the chemistry used to remove the first layer of material, thissecond material is vulnerable to etching, including etching at a higheretch rate than the first material, for example. Here in diagram 202 f, athird process gas comprising conversion molecules 222 (illustrated asshaded diamonds) has been flowed, or is concurrently flowing with thesecond process gas, onto the wafer and these conversion molecules 222convert the exposed surface 220 of the second material into theconverted layer of material. In diagram 202 g, the three molecules ofthe exposed surface 220 of the second material have been converted bythe conversion molecules 222 into a converted layer 224 of material, asillustrated by these three molecules, or converted molecules, havingdark shading. This converted layer 224 is the etch stop layer which iscapable of withstanding the etching chemistry.

In diagram 202 h, the second layer 218 of the first material has beenremoved and the depicted surface of the second material has beenconverted to the converted layer 224 of material, i.e., to convertedmolecules. In some embodiments, the converted layer of material may beremoved, as indicated in diagram 202 i. This removal may include twooperations, a modification operation involving flowing a fourth processgas having other modifying molecules to modify these converted moleculesinto a different volatized molecule, and a removal operation involvingflowing a fifth process gas having other removal molecules (such asmolecules 226 in diagram 202 i. Similar to the other process gases, thefourth and fifth process gases may comprise a carrier gas listed above.Additionally, these modification and removal steps of the convertedlayer 224 may be sequential, overlapping, or simultaneously occurring byusing staggered, overlapping, or co-flows of the fourth and fifthprocess gases.

In some instances, the illustrations in diagrams 202 f and 202 g may beconsidered the creation of an “on the fly” etch stop layer. Once thesecond layer of material is exposed and in the presence of theconversion molecules, the converted layer of material is created “on thefly”. This may allow etching of the first material to continue while theexposed underlying second material is protected with the conversionlayer, i.e., the etch stop layer.

As noted above, in some embodiments, the conversion of the second layerof material may be through a cation exchange between the second layer ofmaterial and the conversion molecules. In some such implementations, thethird process gas supplies a cationic constituent in vapor phase that isexchanged with cationic compounds or constituents in the layer ofmaterial. The cationic constituents of the second material may beconverted to chlorides and thereby volatized as the result of theexchange with the cationic constituent in the third process gas.

For example, the second material may be a zinc oxide, the conversionmolecule may be a zirconium compound, and the conversion of the surfaceof the second material may be a cation exchange of the zinc andzirconium to create a zirconium oxide converted layer of material. Inadditional examples, conversion reactions at a surface of the secondmaterial that comprises zinc may be the following: Example 1, the secondmaterial includes ZnO (solid) and the third process gas includes ZrCl₄(gas) which converts the second material to a converted layer of ZrO₂(solid) and ZnCl₂ (gas) thereby exchanging and removing the zinc;Example 2, the second material includes In₂O₃ (solid) and the thirdprocess gas includes ZrCl₄ (gas) which converts the second material to aconverted layer of ZrO₂ (solid) and InCl₃ (gas) thereby exchanging andremoving the indium; Example 3, the second material includes Ga₂O₃(solid) and the third process gas includes ZrCl₄ (gas) which convertsthe second material to a converted layer of ZrO₂ (solid) and GaCl₃ (gas)thereby exchanging and removing the gallium.

In these examples, the first material may be Al₂O₃ (solid) which can beetched by the primary chemistry, such as HF and trimethylaluminum (TMA).As seen in these examples, the cationic constituents of the secondmaterial, the zinc, indium, and gallium, are converted to chlorides thatare volatilized and therefore removable.

The techniques provided herein may be applicable to wafers with thefirst and second materials that have similar properties. This mayinclude, for example, both materials being oxides, high-k oxides, and/oran oxide and a semiconductor oxide that both may be etched by thechemistry used to etch the first material. Some examples may include analuminum oxide as the first material and a zinc oxide as a secondmaterial.

The techniques provided herein create a converted layer of materialcapable of withstanding, and configured to withstand, the chemistry usedto etch the first material by the converted layer of material being, forinstance, less reactive to the etching chemistry than the second layerof material and the modified layer. This reactivity may be quantifiedaccording to various chemical and physical properties such as etchrates, binding energies, and reactions. In some embodiments, therelationship between the first material, the modified layer of the firstmaterial, the second material, and/or the converted layer of materialmay be quantified with etch rates. For example, the chemistry used toetch the first material may etch the first material, including etchingthe modified layer, at a first etch rate and may also etch the secondmaterial at an unacceptable second etch rate. In some instances, thissecond etch rate may be greater than or equal to the first etch rate,such as at least 50%, 100%, or 200% greater than or equal to the firstetch rate. When exposed to the chemistry for removing the firstmaterial, including the modified layer, the converted layer may have anetch rate less than the first etch rate, including less than or equal to50%, 25%, 15%, 10%, 5%, 2.5%, or 1% of the first etch rate. In oneexample, the chemistry for etching the first material may etch thesecond material at a second etch rate about double the first etch rate,and may etch the converted material at a third etch rate that is lessthan 15% of the first etch rate. In these implementations, the convertedlayer of material is considered capable of withstanding, and configuredto withstand, the chemistry used to etch the first material.

In some embodiments, the relationship between the first material, themodified layer of material, the second material, and/or the convertedlayer of material may be quantified by reaction byproducts. In someinstances, the chemistry used to remove the first material may reactwith the second material and create byproducts, and these byproducts mayremove or otherwise adversely affect the second material. However, theconverted layer of material may, in some such implementations, reactwith the removal chemistry without producing any, or with producinglimited amounts of, byproducts. In some implementations, the convertedlayer of material may not react with, or may have limited reaction with,the removal chemistry. This may prevent, or reduce, the removal of thesecond material. In some instances, the converted layer of material mayalso be considered passive with respect to the removal chemistry.

Returning back to the various techniques provided herein, the thirdprocess gas for converting the exposed surface of the second material toa converted layer may be flowed onto the substrate in various manners.In some implementations, the third process gas may be flowed duringvarious points and/or aspects of an etching process and/or ALE cycle.This may include flowing the third process gas before the modifyingoperation, during the modifying operation, after the modifying operationand before the removal operation, during the removal operation, and/orafter the removal operation. In some such embodiments, a purge gas mayalso be flowed into the chamber after flowing the third process gas andbefore flowing another process gas.

In some implementations, the flow of the third process gas may startduring these noted periods and stop during any of the noted periods oroperations. This may include starting and stopping the flow one or moretimes during an etching process or ALE cycle. For example, in a singleALE cycle, the flow of the third process gas may start before themodifying operation and continue flowing until the end of the removaloperation. In another example, the flow of the third process gas maystart before or at the start of the modifying operation and stop at theend of the modifying operation, and then start again at the start of theremoval operation and stop at the end or after the end of the removaloperation. In yet another example, the flow of the third process gas mayonly start after the modifying operation or at the start of the removaloperation, continue throughout the entire removal operation, and stop atthe end or after the end of the removal operation. In another example,the flow of the third process gas may start during the modifyingoperation, but after this modifying operation has started, and continueuntil the end or after the end of the removal operation. In yet anotherexample, the third process gas may be flowed while the first and secondprocess gas are not flowing, such as before the modifying operation,between the modifying and removal operations, and/or after the removaloperation.

It should be noted that in some embodiments, the flowing of the thirdprocess gas and the converting of the exposed surface of the secondmaterial may not occur concurrently. As noted herein, the convertingoccurs when the surface of the second material is exposed, and the thirdprocess gas may be flowed onto the substrate before and/or when thissurface becomes exposed during the removal operation. For example, thethird process gas may only flow onto the substrate before the removaloperation and not during the removal operation, such as during or afterthe modifying operation, but the third process gas may still be presentduring the removal operation such that the conversion molecules canreact with the surface of the second material when it is uncovered andexposed. This is discussed in more detail below, including with respectto FIGS. 6A-6D.

FIG. 3 depicts another example process flow diagram for performingoperations in accordance with disclosed embodiments. In FIG. 3 , blocks301, 303, and 305 are the same as blocks 101, 103, and 105 in FIG. 1 ,and here the third process gas is co-flowed, or simultaneously flowed,onto the wafer in block 309 during some or all of the modifyingoperation of block 303. Block 309 may start concurrently with, or after,the start of the modifying operation of block 303; in some embodiments,block 309 may start before the start of the modifying operation of block303. In block 307, the surface of the second material is converted tothe converted layer when it is exposed and in the presence of the thirdprocess gas. In some embodiments, the third process gas may beco-flowing during the removal operation of block 305. In some otherembodiments, the third process gas is not flowing during the removaloperation of block 305, but the third process gas is still presentaround the wafer such that when the surface of the second material isuncovered and exposed, it is converted to the converted layer. Anoptional purge may be performed after blocks 303 and/or 309.

FIG. 4A depicts yet another example process flow diagram for performingoperations in accordance with disclosed embodiments. In FIG. 4A, blocks401, 403, and 405 are the same as blocks 101, 103, and 105 in FIG. 1 ,and here the third process gas is co-flowed, or simultaneously flowed,onto the wafer in block 407 during some or all of the removal operationof block 405. Also, in block 407, the surface of the second material isconverted to the converted layer when it is exposed and in the presenceof the third process gas. In some embodiments, block 407 may startconcurrently with, or after, the start of the removal operation of block405; in some embodiments, block 407 may start before the start of theremoval operation of block 405.

FIG. 4B depicts another example process flow diagram for performingoperations in accordance with disclosed embodiments. In FIG. 4B, blocks401, 403, and 405 are the same as in FIG. 4A, and here the third processgas is flowed in between the modification operation of block 403 and theremoval operation of block 405 such that, in some embodiments, the thirdprocess gas is not flowing onto the substrate during blocks 403 and 405.During the removal operation of block 405, similar to block 307 in FIG.3 , block 411 indicates that the surface of the second material isconverted to the converted layer when it is exposed and in the presenceof the third process gas. In some embodiments, an optional purgeoperation may be performed after block 409 and before blocks 405 and411.

Alternatively, or additionally, the third process gas may be flowedduring only a part of the total etching performed on a wafer. This mayinclude, for example, flowing the third process gas after performing anumber N of ALE cycles on the wafer when the total number of ALE cyclesis N+X ALE cycles. This may also include flowing the third process gasafter performing a percentage of the ALE cycles, such after performingat least 10%, 50%, 80%, or 95%, of the total ALE cycles for example.FIG. 5 depicts another example process flow diagram for performingoperations in accordance with disclosed embodiments. Blocks 501, 503,and 505 of FIG. 5 are the same as in FIG. 1 , and here, blocks 503 and505 are repeated for N ALE, or etching, cycles. Once the decision step511 determines that the N ALE cycles have been performed, block 507 isperformed during which the third process gas is flowed onto the waferand the surface of the second material is converted to the convertedlayer when it is exposed and in the presence of the third process gas.This block 507 may be performed for one or more etching cycles after theN cycles are performed. Block 507 may also be performed in any mannerdescribed herein, such as flowing the third process gas during themodifying and/or removal operations, or in-between the modifying andremoval operations as illustrated in FIG. 4B, for example.

Additional illustrations for flowing the third process gas during someetching operations is shown in FIGS. 6A to 6D which depict schematicillustrations of ALE cycles in accordance with disclosed embodiments. Inthese FIGS. 6A through 6D, diagrams 602 a through 602 f depict a waferduring a single ALE cycle. 602 a illustrates the wafer before amodifying operation and corresponds with operation 202 e in FIG. 2 . Forexample, the shaded circles represent the first layer of material andthe white circles represent the second layer of material. 602 billustrates the wafer during a modifying operation, similar to diagram202 b, during which the first process gas comprising a modifyingmolecule 610 is flowed onto the wafer to form modified molecules 614 anda modified layer 618 of the first material. For some thermal ALEimplementations, the modifying of diagram 602 b may be performed whilethe substrate is maintained at a first temperature or first temperaturerange. 602 c illustrates the wafer after the modifying operation ofdiagram 602 b and before the removal operation, and having the modifiedlayer 618.

Diagrams 602 d and 602 e of FIGS. 6A-6D illustrate the wafer during aremoval operation and may correspond with diagrams 202 f and 202 g ofFIG. 2 . In diagram 602 d, the second process gas comprising the removalmolecules 616 is flowed onto the wafer and causes the removal of themodified molecules 614 which uncovers and exposes a surface 620 of thesecond material. Also, in diagram 602 d, the conversion molecules 622are present around the wafer and as illustrated in diagram 602 e, theexposed surface 622 of the second material is converted to the convertedlayer 624 when in the presence of the conversion molecules 622. Indiagram 602 f, the modified layer 624 has been removed and the convertedlayer remains; this may correspond to diagram 202 h of FIG. 2 . Althoughnot shown here, optional separate modification and removal operationsmay be performed to remove the converted layer.

In some embodiments, the removal operations of diagrams 602 d and 602 eof FIGS. 6A-6D may be performed with thermal ALE in which the substrateis maintained at the same, or substantially same, temperature as themodifying operation of diagram 602 b. In some other embodiments, theseremoval operations of diagrams 602 d and 602 e may be performed whilethe substrate is maintained a second temperature or second temperaturerange different than the first temperature or first temperature range ofthe modifying operation of diagram 602 b. Some implementations mayinclude heating or actively cooling the substrate between diagrams 602 band 602 d and 602 e in order to change the substrates temperature. Insome other embodiments, the modification operation of diagram 602 band/or removal operation of diagrams 602 d and 602 e may beplasma-assisted operations.

FIGS. 6A-6D further illustrate various flows of the third process gasonto the wafer. In FIG. 6A, the third process gas having the conversionmolecules 622 is being flowed onto the wafer in at least diagram 602 abefore the modifying operation of 602 b. As shown, the conversionmolecules 622 in FIG. 6A are present during diagrams 602 a-602 e and, insome embodiments, FIG. 6A may illustrate the third process gas flowingduring the whole ALE cycle. In some such embodiments, the third processgas may begin flowing onto the wafer in diagram 602 a before themodification operation of 602 b and continue flowing onto the waferafter the modifying operation in diagram 602 c and during the removaloperation of diagrams 602 d and 602 e. In some embodiments, the thirdprocess gas may only flow during diagram 602 a (which may be consideredflowing while the first and second process gases are not flowing), onlyduring 602 a and 602 b, or only during 602 a, 602 b, and 602 c, and thenstopped, but the third process gas with the conversion moleculesnevertheless remains present in diagrams 602 a-602 e which may beconsidered the whole ALE cycle. For instance, the third process gas mayonly flow during diagrams 602 a and 602 b, and then stopped, but it mayremain present during diagrams 602 c-602 e.

In FIG. 6B, the third process gas having the conversion molecules 622 isflowed onto the substrate during at least a part of the modificationoperation of diagram 602 b. As noted above, the third process gas flowmay start concurrently with, or after, the start of the modifyingoperation. In some embodiments, the third process gas may continueflowing onto the wafer after the modifying operation in diagram 602 cand during the removal operation of diagrams 602 d and 602 e. In someembodiments, the flow of the third process gas may be stopped after themodifying operation and an optional purge may be performed, after whichthe third process gas may not be flowed after, such as during removaloperation of diagrams 602 d and 602 e, but the third process gas maynevertheless still be present. In some other implementations, the flowof the third process gas may be stopped after the modifying operationand an optional purge may be performed and then the flow of the thirdprocess gas may be started before or during the removal operation ofdiagrams 602 d and 602 e. As illustrated, the third process gas havingthe conversion molecules 622 remains present during diagrams 602 b-602 eeven though it may not be flowing during some or all of these diagrams,such as not flowing during 602 d and 602 e, for example. Someembodiments of this FIG. 6B may correspond with the technique of FIG. 3.

In FIG. 6C, the third process gas having the conversion molecules 622 isflowed onto the substrate after the modification operation of diagram602 b and before the removal operation, as shown with the conversionmolecules present in diagram 602 c. In some embodiments, the flow of thethird process gas may be turned off such that it is not flowing duringthe removal operations of diagrams 602 d and 602 e, but is still presentduring these operations; this may be considered flowing while the firstand second process gases are not flowing. Some embodiments of this FIG.6C may correspond with the technique of FIG. 4B. In some embodiments,the third process gas may continue flowing onto the wafer after themodifying operation in diagram 602 c and during the removal operation ofdiagrams 602 d and 602 e.

In FIG. 6D, the third process gas is flowed onto the substrate duringthe removal operation of diagrams 602 d and 602 e. As noted above, thethird process gas flow may start concurrently with, or after, the startof the removal operation. Some embodiments of this FIG. 6D maycorrespond with the technique of FIG. 4A.

Depending on the chemistries involved in the ALE operations, it may beadvantageous to flow the third process gas at various times, includingthose illustrated in FIGS. 6A-6D. For example, the third process gas maybe incompatible with, or have an undesired reaction with, the firstprocess gas and/or the first layer of material. It may therefore beadvantageous to prevent or reduce these unwanted effects by only flowingthe third process gas after the modification operation and/or during theremoval operations illustrated in FIGS. 6C and 6D, for instance. In someother embodiments, there may be limited to no undesirable effects withflowing the third processing gas during the ALE cycle and it maytherefore be flowed during the whole ALE cycle as illustrated in FIG.6A, for example.

In some embodiments, the flow rate of the third process gas may remainconstant. In some other embodiments, it may be advantageous to vary thethird process gas flow rate. This may include, for instance, increasingthe third process gas flowrate during the removal operation in order toprovide more conversion molecules as the removal operation progresses.Some example flow rates may include between about 50 sccm and 1000 sccm.

In some implementations, the conversion of the second layer of materialto an etch stop layer may be considered selectively converting, when thesurface of the second material is uncovered via removal of the modifiedlayer, the surface of the second material to a layer of etch stopmaterial, in which the layer of etch stop material is only positioned ontop of the second material. In some such implementations, during theremoving, the modified layer of the first material and the layer of etchstop material may be exposed to the second process gas and the secondprocess gas may be less reactive with the layer of etch stop materialthan with the modified layer of the first material and the secondmaterial.

In some embodiments, instead of converting a layer of the secondmaterial to a converted layer, a selective deposition may be performedto deposit an etch stop layer onto the second material. This depositionmay, in some instances, be performed after, or concurrently with, aremoval operation. In some embodiments, this selective deposition of alayer of etch stop material may occur when the surface of the secondportion of the second material is uncovered. This selectivity may alsoinclude depositing this layer of etch stop material on the second,uncovered material, while limited to no depositing of this layer of etchstop material occurs on the target, first material. In some embodiments,this may include selectively converting, when the surface of the secondmaterial is uncovered via removal of the modified layer, the surface ofthe second material to a layer of etch stop material, in which the layerof etch stop material is only positioned on top of the second material,such that during the removing, the modified layer of the first materialand the layer of etch stop material are exposed to the second processgas and the second process gas is less reactive with the layer of etchstop material than with the modified layer of the first material and thesecond material.

This deposited etch stop layer may have the same characteristics andproperties of the converted layer described above. This includes thedeposited etch stop layer being capable of withstanding, and configuredto withstand, the chemistry used to etch the first material. This mayfurther include having an etch rate less than the first etch rate (i.e.,the etch rate at which the chemistry removes the first material whichincludes the modified layer), including less than or equal to 50%, 25%,15%, 10%, 5%, 2.5%, or 1% of the first etch rate, a binding energygreater than the binding energy of the modified layer and/or greaterthan or equal to the binding energy of the chemical species used for theremoval, and/or reacting with the removal chemistry without producingany, or with producing limited amounts of, byproducts.

The selective deposition may occur in the same or a different chamber.This selective deposition may be accomplished using various depositionprocesses, such as a chemical vapor deposition (CVD) or atomic layerdeposition (ALD). Some CVD processes may deposit a film on a wafersurface by flowing one or more gas reactants into a reactor which formfilm precursors and by-products. The precursors are transported to thewafer surface where they are adsorbed by the wafer, diffused into thewafer, and deposited on the wafer by chemical reactions, including bythe generation of a plasma in PECVD.

In a typical PECVD reaction, a substrate is heated to an operatingtemperature and exposed to one or more volatile precursors which reactand/or decompose to produce the desired deposit on the substratesurface. The PECVD process generally begins by flowing one or morereactants into the reaction chamber. The reactant delivery may continueas a plasma is generated which exposes the substrate surface to theplasma, which in turn causes deposition to occur on the substratesurface. This process continues until a desired film thickness isreached, after which the plasma is generally extinguished and thereactant flow is terminated. Next, the reaction chamber may be purgedand post-deposition steps may be performed.

Some other deposition processes involve multiple film deposition cycles,each producing a “discrete” film thickness. ALD is one such filmdeposition method, but any technique which puts down thin layers of filmand used in a repeating sequential matter may be viewed as involvingmultiple cycles of deposition. ALD is a film forming technique which iswell-suited to the deposition of conformal films due to the fact that asingle cycle of ALD only deposits a single thin layer of material, thethickness being limited by the amount of one or more film precursorreactants which may adsorb onto the substrate surface (i.e., forming anadsorption-limited layer) prior to the film-forming chemical reactionitself. Multiple “ALD cycles” may then be used to build up a film of thedesired thickness, and since each layer is thin and conformal, theresulting film substantially conforms to the shape of the underlyingdevices structure. In certain embodiments, each ALD cycle includes thefollowing steps: (1) Exposure of the substrate surface to a firstprecursor, (2) purge of the reaction chamber in which the substrate islocated, (3) activation of a reaction of the substrate surface,typically with a plasma and/or a second precursor, and (4) purge of thereaction chamber in which the substrate is located. The duration of eachALD cycle may typically be less than 25 seconds or less than 10 secondsor less than 5 seconds. The plasma exposure step (or steps) of the ALDcycle may be of a short duration, such as a duration of 1 second orless, for example. The plasma may be of other durations longer than that1 second, such as 2 seconds, 5 seconds, or 10 seconds, for instance

Applications

The techniques and apparatuses provided herein may be used for variouschemistries. In one example, the first material may be aluminum oxideand the second material may be a zinc oxide. The aluminum oxide may beetched using a processing gas comprising the removal moleculetrimethylaluminum (TMA) and this TMA may also remove the underlying zincoxide. In order to prevent this zinc oxide removal by the TMA, the thirdprocess gas comprising a zirconium conversion molecule may be flowedonto the wafer to convert a layer of the zinc oxide into a convertedlayer of zirconium oxide which does not react with TMA. In someembodiments, the zirconium conversion molecule may include zirconiumtetrachloride. In some embodiments, this converted layer of zirconiumoxide may be removed by flowing a fourth process gas onto the wafer thatcomprises dimethylaluminum chloride (DMAC). In some instances, thisremoval of the converted layer, or etch stop layer, may also includeflowing hydrogen fluoride (HF) as a modifying operation followed byflowing DMAC in the removal operation.

As also noted above, another example may include aluminum oxide coveringthe second material that is indium gallium zinc oxide (IGZO). To etchthis aluminum oxide, a first process gas containing hydrogen fluoride(HF) may be used for the modifying operation, and the removal moleculemay include TMA which again may remove the underlying IGZO. The thirdprocess gas therefore may include zirconium, such as a zirconiumchloride, e.g., ZrCl₄ or ZrCl₄, orTetrakis(ethylmethylamino)zirconium(IV) (TEMAZ), to convert the surfaceof the exposed IGZO to a zirconium oxide, such as ZrO₂ (solid) or ZrO₂.During this example and the above example, etching of the aluminum oxidelayer may continue during the conversion reactions.

ALE Apparatuses

Referring now to FIG. 7 , an example of a substrate processing chamber720 for selectively etching materials according to the presentdisclosure is shown. While a specific substrate processing chamber isshown and described, the methods described herein may be implemented onother types of substrate processing systems. FIG. 7 depicts an exampleapparatus 720 for semiconductor processing in accordance with disclosedembodiments, including thermal atomic layer etching; this apparatus 720includes a processing chamber 722, a process gas unit 724, a substrateheating unit 726, and a substrate cooling unit 728. The processingchamber 722 has chamber walls 730 that at least partially bound anddefine a chamber interior 732 (which may be considered a plenum volume).The process gas unit 724 is configured to flow process gases, which mayinclude liquids and/or gases, such as a reactant, modifying molecules,converting molecules, or removal molecules, onto a substrate 734 in thechamber interior 732. The process gas unit 724 also includes one or moreflow features 742 configured to flow the first process gas onto thesubstrate 734, such as a hole, a nozzle (two of which are depicted), ora showerhead. The one or more flow features 742 may be positioned above,below, on the side, or a combination of positions, within the chamberinterior 732, such as on the processing chamber walls, top, and bottom,for instance. The process gas unit 724 may include a mixing vessel forblending and/or conditioning process gases for delivery to the chamberinterior 732. One or more mixing vessel inlet valves may controlintroduction of process gases to the mixing vessel.

The process gas unit 724 may include a first process gas source 736, afirst process liquid source 738, a vaporization point (not depicted)which may vaporize the first liquid into a gas, and a carrier gas source740. Some reactants may be stored in liquid form prior to vaporizationand subsequent to delivery to the process chamber 722. The first processgas may comprise an oxidizing gas, a halogenating gas, or another gasconfigured to modify one or more layers of material on the substrate,without using a plasma, in some embodiments. In some implementations,the vaporization point may be a heated liquid injection module. In someother implementations, the vaporization point may be a heated vaporizer.In yet other implementations, the vaporization point may be eliminatedfrom the process station. In some implementations, a liquid flowcontroller (LFC) upstream of the vaporization point may be provided forcontrolling a mass flow of liquid for vaporization and delivery to thechamber interior 732. The carrier gas source 740 includes one or morecarrier gases or liquids that may be flowed with the processing gas;these may be inert gases like N₂, Ar, Ne, He. The apparatus 720 may alsoinclude a vacuum pump 733 configured to pump the chamber interior to lowpressures, such as a vacuum having a pressure of 1 mTorr or 10 Torr, forexample.

The chamber interior 732 includes substrate support features 735 thatare configured to support and thermally float a substrate 734 in thechamber. The substrate support features 735 may include clamps,horizontal pins or supports, vertical pins or supports, andsemi-circular rings, for instance, that support the substrate 734 in thechamber interior 732. These features are configured to support thesubstrate 734 such that the thermal mass of the substrate 734 is reducedas much as possible to the thermal mass of just the substrate. Eachsubstrate support feature 735 may therefore have minimal contact withthe substrate 734 and may be the smallest number of features required toadequately support the substrate during processing (e.g., in order tosupport the weight of the substrate and prevent inelastic deformation ofthe substrate). For instance, the surface area of one substrate supportfeature 735 in contact with a substrate may be less than about 1%, 0.5%,0.1%, 0.05%, or 0.01% of the overall surface area of the back side ofthe substrate; also, for instance, 2, 3, or 4 features may be utilized.

In one example, the support features 735 may include two or morevertical pins that have grooves wrapped or spiraled along the vertical,longitudinal axis and that are offset at varying distances from thelongitudinal axis and configured to support a substrate. When thevertical pin rotates along its longitudinal axis and the edge of asubstrate is positioned in the groove, the edge of the groove, andtherefore the edge of the substrate, moves farther away from thelongitudinal axis. When multiple vertical pins are used to support asubstrate, the rotation of the vertical pins causes the grooves to applya supporting force to the substrate in a direction perpendicular to thelongitudinal axis.

In some embodiments, the chamber 722 may include a wafer supportpedestal that includes substrate lift pins. During thermal ALEprocessing, the lift pins may support and position the substrate awayfrom the pedestal such that there is substantially no transference ofthermal energy between the pedestal and substrate (e.g., less than 10%,5%, 1%, 0.5%, or 0.1% of energy transferred between the two). In someother embodiments, the chamber 722 may not have a pedestal. In someembodiments, an electrostatic chuck (ESC) may be used that containssubstrate heating unit 726 configured to heat the substrate totemperatures provided herein, such as between about 20° C. and 500° C.

The substrate heating unit 726 is configured to heat the substrate tomultiple temperatures and maintain such temperatures for at least 1second, 5 seconds, 10 seconds, 30 seconds, 1 minute, 2 minutes, or 3minutes, for example. In some embodiments, the substrate heating unit726 is configured to heat the substrate between at least two temperatureranges, with the first range between about 20° C. and 150° C., and thesecond range between about 200° C. and 600° C., as well as configured tomaintain the substrate at a temperature within these ranges for at least1 second, 5 seconds, or 10 seconds, for example. Additionally, in someembodiments, the substrate heating unit 726 is configured to heat thesubstrate from the first temperature range to the second temperaturerange in less than about 250 milliseconds, 150 milliseconds, 100milliseconds, or 50 milliseconds, for instance.

The substrate heating unit 726 may utilize radiant heating, convectiveheating, laser heating, plasma heating, solid-to-solid thermaltransference, or a combination of these items. For radiant heating, thesubstrate heating unit 726 may be used for emitted light heating,infrared heating, ultraviolet heating, microwave heating, radiofrequency heating, and induction heating. For example, the substrateheating unit 726 may include light emitting diodes (LEDs) that emitvisible light with wavelengths that may include and range between 400nanometers (nm) and 800 nm. In another example, the infrared heating mayuse one or more infrared emitters that emit infrared radiation in the780 nanometer (nm) to 1400 nm range (e.g., a near infrared heater), inthe 1400 nm and 3000 nm range (e.g., a medium infrared heater), and 3000nm or above (e.g., a far infrared heater), for instance. This may alsoinclude, for instance, a heat lamp, light emitting diodes (e.g., LEDs),a ceramic heater, a quartz heater, or a plurality of Gradient Index(GRIN) Lenses connected to a light energy source. A GRIN lens isconfigured to deliver heat energy (thermal or light) from the lightenergy source to the substrate in a uniform manner; the light source maybe a laser or high-intensity light source that transmits the heat energythrough a conduit, such as a fiber optic cable, to the GRIN lenses. Theheating elements utilized by the substrate heating unit 726 may bepositioned above, below, on the side, or a combination of the positions,the substrate 734, and they may be positioned inside, outside, or both,the chamber interior 732. In FIG. 7 , the heating elements utilized bythe substrate heating unit 726 include a plurality of LEDs 726A that arepositioned both above and below the substrate 734; the lower heatingelements are positioned inside the chamber interior 732 and the upperheating elements are positioned outside the chamber interior 732. Insome embodiments, for some of the heating elements that are positionedoutside the chamber 722, the chamber 722 may have a window 754 thatallows for the radiation to be transmitted into the chamber interior 732and onto the substrate 734. In some embodiments, this window 754 may bean optical-grade quartz plate while in other embodiments it may be atransparent indium tin oxide (ITO) window. In some embodiments, thesubstrate heating unit 726 include a plurality of LEDs 726A may only bepositioned underneath the substrate 734, which may include inside apedestal or ESC that also may include a window through which the lightemitted by the LEDs may reach the backside of the substrate.

For convective heating, the substrate heating unit 726 may flow aheating gas into the chamber interior 732 in order to heat thesubstrate. The substrate heating unit 726 may include a heating gassource, a heating unit configured to heat the heating gas to a desiredtemperature, such as at least 20° C., 100° C., 250° C., 350° C., 500°C., and 600° C., and heating flow features, such as nozzles or holes,that allow for the heating gas to flow into the chamber interior 732 andonto the substrate 734. These heating flow features may be positionedabove, below, on the side of, or a combination, the substrate.

For laser heating, the substrate heating unit 726 may have one or morelasers that are configured to heat the substrate in the chamberinterior. These lasers may be stationary or configured to move (e.g., ascanning laser), and they may be positioned above, below, or both, thesubstrate; the lasers may also be positioned inside, outside, or both,of the chamber interior. Similar to the radiant heating discussed above,for lasers that are positioned outside the chamber interior, the chambermay include a window that enables the light emissions of the laser toreach the substrate.

For plasma heating, the substrate heating unit 726 may have featuresconfigured to generate and maintain a plasma in the chamber interior toheat the substrate. Features that may generate a plasma are discussed inmore detail below. In addition, in some embodiments, the chamberinterior may include vertical pins that are positioned below thesubstrate and configured to support the wafer. During heating of thesubstrate, it may be supported by only the vertical pins and a plasmamay be generated between the bottom of the substrate and a surface belowthe substrate, such as the bottom wall of the chamber or a wafer supportpedestal. This plasma may heat and maintain the temperature of thesubstrate to the desired temperatures.

For solid-to-solid thermal transference, the substrate heating unit 726may have one or more heating surfaces that are configured to contact andheat the substrate in the chamber interior. In some embodiments, thesubstrate heating unit 726 may have a heating platen, such as a flatsurface or a surface of a substrate pedestal, that is configured tocontact the back surface of the substrate and heat the substrate. Thisheating platen may have heating elements such as a heating coil, heatingfluid, or radiative heating discussed above, that may heat the surfaceof the heating platen. The substrate may be heated when the back of thesubstrate is in direct contact with, or is offset from the heatingplaten but close enough to receive thermal energy from, the heatingplaten. When using this solid-to-solid thermal transference to heat thesubstrate, the substrate is separated from the heating platen when it iscooled. While some conventional ALE apparatuses may have a substratepedestal that includes both heating and cooling elements, theseapparatuses are unable to quickly (e.g., under 250 milliseconds) cyclebetween the temperatures of thermal ALE because of the large thermalmasses of the pedestal that are repeatedly heated and cooled. Forinstance, it may take multiple seconds or minutes to heat a pedestalfrom a first temperature range (e.g., 20° C. to 100° C.) to a secondtemperature range (e.g., 200° C. to 500° C.), as well as to cool thepedestal from the second temperature range to a lower temperature thatcan cool the substrate to the first temperature range. Accordingly,after using this solid-to-solid heating technique, the heating platenand the substrate are separated from each other which may beaccomplished, for instance, by moving the substrate and/or the heatingplaten away from each other. Without this separation, cooling occurs ofboth the thermal mass of the substrate and the heating platen whichincreases the cooling time which decreases substrate throughput. In someembodiments, an ESC or pedestal having the substrate heating unit and aPeltier element for cooling may enable fast heating and cooling times(such as about 30 seconds to cool a substrate to a desired temperature).

The substrate cooling unit 728 of FIG. 7 is configured to actively coolthe substrate. In some embodiments, the substrate cooling unit 728 flowsa cooling gas onto the substrate 734 which actively cools the substrate734. The substrate cooling unit 728 may include a cooling fluid source748 which may contain a cooling fluid (a gas or a liquid), and a cooler750 configured to cool the cooling fluid to a desired temperature, suchas less than or equal to 0° C., −50° C., −100° C., −150° C., −170° C.,−200° C., and −250° C., for instance. The substrate cooling unit 728includes piping and coolant flow features 752, e.g., nozzles or holes,that are configured to flow the coolant fluid into the chamber interior732. In some embodiments, the fluid may be in liquid state when it isflowed to the chamber 722 and may turn to a vapor state when it reachesthe chamber interior 732, for example if the chamber interior 732 is ata low pressure state, such as 1 Torr, for instance. The cooling fluidmay be an inert element, such as nitrogen, argon, helium. In someembodiments, the flow rate of the cooling fluid into the chamberinterior 732 may be at least 10 liters per second, 50 liters per second,100 liters per second, 150 liters per second, 200 liters per second, 250liters per second, and 300 liters per second, for example.

Various factors may increase the ability of the cooling fluid to coolthe substrate. It has been discovered through various experiments thatthe higher the flow rate of the cooling fluid, the faster the substrateis cooled. In one example experiment, a cooling gas at about −196° C.flowed onto a substrate at a flow rate of 1 liter per second was foundto reduce the temperature of a substrate from about 220° C. to about215° C. in about 5,000 milliseconds, while the same cooling gas a flowrate of 10 liters per second reduced the temperature of a substrate fromabout 220° C. to about 195° C. in about 5,000 milliseconds. It was alsodiscovered that a gap (1052 in FIG. 10 ) between the substrate and thetop of the chamber may also affect the cooling of the substrate; thesmaller the gap, the higher the cooling. In one instance, it wasdiscovered that a substrate separated from the top of the chamber by agap of about 50 micrometers was cooled from about 220° C. to about 215°C. in about 5,000 milliseconds using a cooling gas at about −196° C.,while a substrate separated from the top of the chamber by a gap ofabout 5 millimeters was cooled from about 220° C. to about 20TC in about5,000 milliseconds using the same cooling gas. Accordingly, it wasdiscovered that the higher the flow rate and the smaller the gap, thefaster the substrate is cooled.

In some embodiments, the substrate cooling unit 728 may usesolid-to-solid thermal transference to actively cool the substrate 734.In some of these embodiments, a cooling platen, such as a flat, cooledsurface may be used to contact the bottom of the substrate and cool thesubstrate. This platen may be cooled by flowing a cooling fluid on,through, or underneath the platen. When using this solid-to-solidcooling, similar to the solid-to-solid heating discussed above, thesubstrate is separated from the cooling platen during heating of thesubstrate, such as by moving the substrate away from the cooling platenby, for instance, raising it up with lift pins. Without this separation,both the thermal masses of the substrate and cooling platen are cooledwhich requires more cooling that in turn increases process time anddecreases throughput. In some embodiments, radiant heating of the top ofthe substrate or plasma heating of the bottom of the substrate may beused in conjunction with solid-to-solid cooling.

In some embodiments, the substrate cooling unit 728 may use lasercooling to cool the substrate. This may enable the cooling of asubstrate that includes thulium molecules on at least the exposedsurface of the substrate by utilizing a reverse Navier-Stokes reaction.For example, the temperature of the substrate manifests itself inphonons and the laser cooling emits photons to the substrate surfacewhich interact with and pick-up phonons in the thulium, and then leavethe substrate with the phonon from the thulium at a higher energy level.The removal of these phonons causes a decrease in the temperature of thesubstrate. The thulium may be doped onto the surface of the substrate inorder to enable this laser cooling, and this doping may be incorporatedinto the techniques listed above, such as occurring after or before anyoperation, such as the removal operation.

As noted above, some embodiments of the apparatus may include a plasmasource configured to generate a plasma within the chamber interior.These plasma sources may be a capacitively coupled plasma (CCP), aninductively coupled plasma (ICP), an upper remote plasma, and a lowerremote plasma.

In some embodiments, the apparatuses described herein may include acontroller that is configured to control various aspects of theapparatus in order to perform the techniques described herein. Forexample, in FIG. 7 , apparatus 720 includes a controller 766 (which mayinclude one or more physical or logical controllers) that iscommunicatively connected with and that controls some or all of theoperations of a processing chamber. The system controller 766 mayinclude one or more memory devices 768 and one or more processors 770.In some embodiments, the apparatus includes a switching system forcontrolling flow rates and durations, the substrate heating unit, thesubstrate cooling unit, the loading and unloading of a substrate in thechamber, the thermal floating of the substrate, and the process gasunit, for instance, when disclosed embodiments are performed. In someembodiments, the apparatus may have a switching time of up to about 500ms, or up to about 750 ms. Switching time may depend on the flowchemistry, recipe chosen, reactor architecture, and other factors.

In some implementations, the controller 766 is part of an apparatus or asystem, which may be part of the above-described examples. Such systemsor apparatuses can include semiconductor processing equipment, includinga processing tool or tools, chamber or chambers, a platform or platformsfor processing, and/or specific processing components (a gas flowsystem, a substrate heating unit, a substrate cooling unit, etc.). Thesesystems may be integrated with electronics for controlling theiroperation before, during, and after processing of a semiconductor waferor substrate. The electronics may be referred to as the “controller,”which may control various components or subparts of the system orsystems. The controller 766, depending on the processing parametersand/or the type of system, may be programmed to control any of theprocesses disclosed herein, including the delivery of processing gases,temperature settings (e.g., heating and/or cooling), pressure settings,vacuum settings, power settings, radio frequency (RF) generatorsettings, RF matching circuit settings, frequency settings, flow ratesettings, fluid delivery settings, positional and operation settings,wafer transfers into and out of a tool and other transfer tools and/orload locks connected to or interfaced with a specific system.

Broadly speaking, the controller 766 may be defined as electronicshaving various integrated circuits, logic, memory, and/or software thatreceive instructions, issue instructions, control operation, enablecleaning operations, enable endpoint measurements, and the like. Theintegrated circuits may include chips in the form of firmware that storeprogram instructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing operations duringthe fabrication of one or more layers, materials, metals, oxides,silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer.

The controller 766, in some implementations, may be a part of or coupledto a computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing operations to follow a current processing,or to start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller 766 receivesinstructions in the form of data, which specify parameters for each ofthe processing operations to be performed during one or more operations.It should be understood that the parameters may be specific to the typeof process to be performed and the type of tool that the controller isconfigured to interface with or control. Thus as described above, thecontroller 766 may be distributed, such as by comprising one or morediscrete controllers that are networked together and working towards acommon purpose, such as the processes and controls described herein. Anexample of a distributed controller for such purposes would be one ormore integrated circuits on a chamber in communication with one or moreintegrated circuits located remotely (such as at the platform level oras part of a remote computer) that combine to control a process on thechamber.

As noted above, depending on the process operation or operations to beperformed by the apparatus, the controller 766 might communicate withone or more of other apparatus circuits or modules, other toolcomponents, cluster tools, other tool interfaces, adjacent tools,neighboring tools, tools located throughout a factory, a main computer,another controller, or tools used in material transport that bringcontainers of wafers to and from tool locations and/or load ports in asemiconductor manufacturing factory.

As also stated above, the controller is configured to perform anytechnique described above. For instance, referring to apparatus 720 ofFIG. 7 and technique of FIG. 1 , in some embodiments the controller 766is configured to cause the substrate heating unit 726 to bring (i.e.,heat or actively cool) the substrate 734 positioned on the substratesupport features 735 to a first temperature, and cause the process gasunit 724 to flow the first process gas to the substrate 734. As notedabove, the first process gas is configured to modify one or more surfacelayers of material on the substrate 734 by chemical adsorption, withoutusing a plasma in some embodiments, while the substrate is maintained atthe first temperature. The controller 766 may further be configured tocause, after the modifying, the substrate heating unit 726 to maintainthe substrate 734 at the second temperature and the one or more modifiedsurface layers on the substrate 734 may be removed by desorption whilethe substrate 734 is maintained at the second temperature. Thecontroller 766 may further be configured to cause the process gas unit724 to flow the third process gas onto the substrate as described hereinto convert the exposed surface of the second material into the convertedlayer of material, i.e., the etch stop layer.

FIGS. 8A-8C illustrate an embodiment of an adjustable gap capacitivelycoupled confined RF plasma reactor 800 that may be used for performingthe etching operations described herein. As depicted, a vacuum chamber802 includes a chamber housing 804, surrounding an interior spacehousing a lower electrode 806. In an upper portion of the chamber 802 anupper electrode 808 is vertically spaced apart from the lower electrode806. Planar surfaces of the upper and lower electrodes 808, 806 aresubstantially parallel and orthogonal to the vertical direction betweenthe electrodes. Preferably the upper and lower electrodes 808, 806 arecircular and coaxial with respect to a vertical axis. A lower surface ofthe upper electrode 808 faces an upper surface of the lower electrode806. The spaced apart facing electrode surfaces define an adjustable gap810 therebetween. During operation, the lower electrode 806 is suppliedRF power by an RF power supply (match) 820. RF power is supplied to thelower electrode 806 though an RF supply conduit 822, an RF strap 824 andan RF power member 826. A grounding shield 836 may surround the RF powermember 826 to provide a more uniform RF field to the lower electrode806. As described in commonly-owned U.S. Pat. No. 7,732,728, the entirecontents of which are herein incorporated by reference, a wafer isinserted through wafer port 882 and supported in the gap 810 on thelower electrode 806 for processing, a process gas is supplied to the gap810 and excited into plasma state by the RF power. The upper electrode808 can be powered or grounded.

In the embodiment shown in FIGS. 8A-8C, the lower electrode 806 issupported on a lower electrode support plate 816. An insulator ring 814interposed between the lower electrode 806 and the lower electrodesupport plate 816 insulates the lower electrode 806 from the supportplate 816.

An RF bias housing 830 supports the lower electrode 806 on an RF biashousing bowl 832. The bowl 832 is connected through an opening in achamber wall plate 818 to a conduit support plate 838 by an arm 834 ofthe RF bias housing 830. In a preferred embodiment, the RF bias housingbowl 832 and RF bias housing arm 834 are integrally formed as onecomponent, however, the arm 834 and bowl 832 can also be two separatecomponents bolted or joined together.

The RF bias housing arm 834 includes one or more hollow passages forpassing RF power and facilities, such as gas coolant, liquid coolant, RFenergy, cables for lift pin control, electrical monitoring and actuatingsignals from outside the vacuum chamber 802 to inside the vacuum chamber802 at a space on the backside of the lower electrode 806. The RF supplyconduit 822 is insulated from the RF bias housing arm 834, the RF biashousing arm 834 providing a return path for RF power to the RF powersupply 820. A facilities conduit 840 provides a passageway for facilitycomponents. Further details of the facility components are described inU.S. Pat. Nos. 5,948,704 and 7,732,728 and are not shown here forsimplicity of description. The gap 810 is preferably surrounded by aconfinement ring assembly or shroud (not shown), details of which can befound in commonly owned published U.S. Pat. No. 7,740,736 hereinincorporated by reference. The interior of the vacuum chamber 802 ismaintained at a low pressure by connection to a vacuum pump throughvacuum portal 880.

The conduit support plate 838 is attached to an actuation mechanism 842.The actuation mechanism 842, such as a servo mechanical motor, steppermotor or the like is attached to a vertical linear bearing 844, forexample, by a screw gear 846 such as a ball screw and motor for rotatingthe ball screw. During operation to adjust the size of the gap 810, theactuation mechanism 842 travels along the vertical linear bearing 844.FIG. 8A illustrates the arrangement when the actuation mechanism 842 isat a high position on the linear bearing 844 resulting in a small gap810 a. FIG. 8B illustrates the arrangement when the actuation mechanism842 is at a mid position on the linear bearing 844. As shown, the lowerelectrode 806, the RF bias housing 830, the conduit support plate 838,the RF power supply 820 have all moved lower with respect to the chamberhousing 804 and the upper electrode 808, resulting in a medium size gap810 b.

FIG. 8C illustrates a large gap 810 c when the actuation mechanism 842is at a low position on the linear bearing. Preferably, the upper andlower electrodes 808, 806 remain co-axial during the gap adjustment andthe facing surfaces of the upper and lower electrodes across the gapremain parallel.

This embodiment allows the gap 810 between the lower and upperelectrodes 806, 808 in the CCP chamber 802 during multi-step processrecipes (BARC, HARC, and STRIP etc.) to be adjusted, for example, inorder to maintain uniform etch across a large diameter substrate such as300 mm wafers or flat panel displays. In particular, this chamberpertains to a mechanical arrangement that permits the linear motionnecessary to provide the adjustable gap between lower and upperelectrodes 806, 808.

FIG. 8A illustrates laterally deflected bellows 850 sealed at aproximate end to the conduit support plate 838 and at a distal end to astepped flange 828 of chamber wall plate 818. The inner diameter of thestepped flange defines an opening 812 in the chamber wall plate 818through which the RF bias housing arm 834 passes. The distal end of thebellows 850 is clamped by a clamp ring 852.

The laterally deflected bellows 850 provides a vacuum seal whileallowing vertical movement of the RF bias housing 830, conduit supportplate 838 and actuation mechanism 842. The RF bias housing 830, conduitsupport plate 838 and actuation mechanism 842 can be referred to as acantilever assembly. Preferably, the RF power supply 820 moves with thecantilever assembly and can be attached to the conduit support plate838. FIG. 8B shows the bellows 850 in a neutral position when thecantilever assembly is at a mid position. FIG. 8C shows the bellows 850laterally deflected when the cantilever assembly is at a low position.

A labyrinth seal 848 provides a particle barrier between the bellows 850and the interior of the plasma processing chamber housing 804. A fixedshield 856 is immovably attached to the inside inner wall of the chamberhousing 804 at the chamber wall plate 818 so as to provide a labyrinthgroove 860 (slot) in which a movable shield plate 858 moves verticallyto accommodate vertical movement of the cantilever assembly. The outerportion of the movable shield plate 858 remains in the slot at allvertical positions of the lower electrode 806.

In the embodiment shown, the labyrinth seal 848 includes a fixed shield856 attached to an inner surface of the chamber wall plate 818 at aperiphery of the opening 812 in the chamber wall plate 818 defining alabyrinth groove 860. The movable shield plate 858 is attached andextends radially from the RF bias housing arm 834 where the arm 834passes through the opening 812 in the chamber wall plate 818. Themovable shield plate 858 extends into the labyrinth groove 860 whilespaced apart from the fixed shield 856 by a first gap and spaced apartfrom the interior surface of the chamber wall plate 818 by a second gapallowing the cantilevered assembly to move vertically. The labyrinthseal 848 blocks migration of particles spalled from the bellows 850 fromentering the vacuum chamber interior 805 and blocks radicals fromprocess gas plasma from migrating to the bellows 850 where the radicalscan form deposits which are subsequently spalled.

FIG. 8A shows the movable shield plate 858 at a higher position in thelabyrinth groove 860 above the RF bias housing arm 834 when thecantilevered assembly is in a high position (small gap 810 a). FIG. 8Cshows the movable shield plate 858 at a lower position in the labyrinthgroove 860 above the RF bias housing arm 834 when the cantileveredassembly is in a low position (large gap 810 c). FIG. 8B shows themovable shield plate 858 in a neutral or mid position within thelabyrinth groove 860 when the cantilevered assembly is in a mid position(medium gap 810 b). While the labyrinth seal 848 is shown as symmetricalabout the RF bias housing arm 834, in other embodiments the labyrinthseal 848 may be asymmetrical about the RF bias arm 834.

FIG. 9 depicts a semiconductor process cluster architecture with variousmodules that interface with a vacuum transfer module 938 (VTM). Thearrangement of transfer modules to “transfer” substrates among multiplestorage facilities and processing modules may be referred to as a“cluster tool architecture” system. Airlock 930, also known as aloadlock or transfer module, is shown in VTM 938 with four processingmodules 920 a-920 d, which may be individually optimized to performvarious fabrication processes. By way of example, processing modules 920a-920 d may be implemented to perform substrate etching, deposition, ionimplantation, substrate cleaning, sputtering, and/or other semiconductorprocesses as well as laser metrology and other defect detection anddefect identification methods. One or more of the processing modules(any of 920 a-920 d) may be implemented as disclosed herein, i.e., foretching recessed features into substrates. Airlock 930 and processmodules 920 a-920 d may be referred to as “stations.” Each station has afacet 936 that interfaces the station to VTM 938. Inside the facets,sensors 1-18 are used to detect the passing of substrate 926 when movedbetween respective stations.

Robot 922 transfers substrates between stations. In one implementation,the robot may have one arm, and in another implementation, the robot mayhave two arms, where each arm has an end effector 924 to pick substratesfor transport. Front-end robot 932, in atmospheric transfer module (ATM)940, may be used to transfer substrates from cassette or Front OpeningUnified Pod (FOUP) 934 in Load Port Module (LPM) 942 to airlock 930.Module center 928 inside process modules 920 a-920 d may be one locationfor placing the substrate. Aligner 944 in ATM 940 may be used to alignsubstrates.

In an exemplary processing method, a substrate is placed in one of theFOUPs 934 in the LPM 942. Front-end robot 932 transfers the substratefrom the FOUP 934 to the aligner 944, which allows the substrate 926 tobe properly centered before it is etched, or deposited upon, orotherwise processed. After being aligned, the substrate is moved by thefront-end robot 932 into an airlock 930. Because airlock modules havethe ability to match the environment between an ATM and a VTM, thesubstrate is able to move between the two pressure environments withoutbeing damaged. From the airlock module 930, the substrate is moved byrobot 922 through VTM 938 and into one of the process modules 920 a-920d, for example process module 920 a. In order to achieve this substratemovement, the robot 922 uses end effectors 924 on each of its arms. Inprocess module 920 a, the substrate undergoes etching as described.Next, the robot 922 moves the substrate out of processing module 920 ato its next desired position.

It should be noted that the computer controlling the substrate movementcan be local to the cluster architecture, or can be located external tothe cluster architecture in the manufacturing floor, or in a remotelocation and connected to the cluster architecture via a network.

Deposition Apparatuses

FIG. 10 schematically shows an embodiment of a process station 1000 thatmay be used to deposit material using atomic layer deposition (ALD)and/or chemical vapor deposition (CVD), either of which may be plasmaenhanced. For simplicity, the process station 1000 is depicted as astandalone process station having a process chamber body 1002 formaintaining a low-pressure environment. However, it will be appreciatedthat a plurality of process stations 1000 may be included in a commonprocess tool environment. Further, it will be appreciated that, in someembodiments, one or more hardware parameters of process station 1000,including those discussed in detail below, may be adjustedprogrammatically by one or more computer controllers.

Process station 1000 fluidly communicates with reactant delivery system1001 for delivering process gases to a distribution showerhead 1006.Reactant delivery system 1001 includes a mixing vessel 1004 for blendingand/or conditioning process gases for delivery to showerhead 1006. Oneor more mixing vessel inlet valves 1020 may control introduction ofprocess gases to mixing vessel 1004. Similarly, a showerhead inlet valve1005 may control introduction of process gasses to the showerhead 1006.

Some reactants, like BTBAS, may be stored in liquid form prior tovaporization at and subsequent delivery to the process station. Forexample, the embodiment of FIG. 10 includes a vaporization point 1003for vaporizing liquid reactant to be supplied to mixing vessel 1004. Insome embodiments, vaporization point 1003 may be a heated vaporizer. Thereactant vapor produced from such vaporizers may condense in downstreamdelivery piping. Exposure of incompatible gases to the condensedreactant may create small particles. These small particles may clogpiping, impede valve operation, contaminate substrates, etc. Someapproaches to addressing these issues involve sweeping and/or evacuatingthe delivery piping to remove residual reactant. However, sweeping thedelivery piping may increase process station cycle time, degradingprocess station throughput. Thus, in some embodiments, delivery pipingdownstream of vaporization point 1003 may be heat traced. In someexamples, mixing vessel 1004 may also be heat traced. In onenon-limiting example, piping downstream of vaporization point 1003 hasan increasing temperature profile extending from approximately 100° C.to approximately 150° C. at mixing vessel 1004.

In some embodiments, reactant liquid may be vaporized at a liquidinjector. For example, a liquid injector may inject pulses of a liquidreactant into a carrier gas stream upstream of the mixing vessel. In onescenario, a liquid injector may vaporize reactant by flashing the liquidfrom a higher pressure to a lower pressure. In another scenario, aliquid injector may atomize the liquid into dispersed microdroplets thatare subsequently vaporized in a heated delivery pipe. It will beappreciated that smaller droplets may vaporize faster than largerdroplets, reducing a delay between liquid injection and completevaporization. Faster vaporization may reduce a length of pipingdownstream from vaporization point 1003. In one scenario, a liquidinjector may be mounted directly to mixing vessel 1004. In anotherscenario, a liquid injector may be mounted directly to showerhead 1006.

In some embodiments, a liquid flow controller upstream of vaporizationpoint 1003 may be provided for controlling a mass flow of liquid forvaporization and delivery to process station 1000. For example, theliquid flow controller (LFC) may include a thermal mass flow meter (MFM)located downstream of the LFC. A plunger valve of the LFC may then beadjusted responsive to feedback control signals provided by aproportional-integral-derivative (PID) controller in electricalcommunication with the MFM. However, it may take one second or more tostabilize liquid flow using feedback control. This may extend a time fordosing a liquid reactant. Thus, in some embodiments, the LFC may bedynamically switched between a feedback control mode and a directcontrol mode. In some embodiments, the LFC may be dynamically switchedfrom a feedback control mode to a direct control mode by disabling asense tube of the LFC and the PID controller.

Showerhead 1006 distributes process gases toward substrate 1012. In theembodiment shown in FIG. 10 , substrate 1012 is located beneathshowerhead 1006, and is shown resting on a pedestal 1008. It will beappreciated that showerhead 1006 may have any suitable shape, and mayhave any suitable number and arrangement of ports for distributingprocesses gases to substrate 1012.

In some embodiments, a microvolume 1007 is located beneath showerhead1006. Performing an ALD and/or CVD process in a microvolume rather thanin the entire volume of a process station may reduce reactant exposureand sweep times, may reduce times for altering process conditions (e.g.,pressure, temperature, etc.), may limit an exposure of process stationrobotics to process gases, etc. Example microvolume sizes include, butare not limited to, volumes between 0.1 liter and 2 liters. Thismicrovolume also impacts productivity throughput. While deposition rateper cycle drops, the cycle time also simultaneously reduces. In certaincases, the effect of the latter is dramatic enough to improve overallthroughput of the module for a given target thickness of film.

In some embodiments, pedestal 1008 may be raised or lowered to exposesubstrate 1012 to microvolume 1007 and/or to vary a volume ofmicrovolume 1007. For example, in a substrate transfer phase, pedestal1008 may be lowered to allow substrate 1012 to be loaded onto pedestal1008. During a deposition process phase, pedestal 1008 may be raised toposition substrate 1012 within microvolume 1007. In some embodiments,microvolume 1007 may completely enclose substrate 1012 as well as aportion of pedestal 1008 to create a region of high flow impedanceduring a deposition process.

Optionally, pedestal 1008 may be lowered and/or raised during portionsthe deposition process to modulate process pressure, reactantconcentration, etc., within microvolume 1007. In one scenario whereprocess chamber body 1002 remains at a base pressure during thedeposition process, lowering pedestal 1008 may allow microvolume 1007 tobe evacuated. Example ratios of microvolume to process chamber volumeinclude, but are not limited to, volume ratios between 1:900 and 1:10.It will be appreciated that, in some embodiments, pedestal height may beadjusted programmatically by a suitable computer controller.

In another scenario, adjusting a height of pedestal 1008 may allow aplasma density to be varied during plasma activation and/or treatmentcycles included in the deposition process. At the conclusion of thedeposition process phase, pedestal 1008 may be lowered during anothersubstrate transfer phase to allow removal of substrate 1012 frompedestal 1008.

While the example microvolume variations described herein refer to aheight-adjustable pedestal, it will be appreciated that, in someembodiments, a position of showerhead 1006 may be adjusted relative topedestal 1008 to vary a volume of microvolume 1007. Further, it will beappreciated that a vertical position of pedestal 1008 and/or showerhead1006 may be varied by any suitable mechanism within the scope of thepresent disclosure. In some embodiments, pedestal 1008 may include arotational axis for rotating an orientation of substrate 1012. It willbe appreciated that, in some embodiments, one or more of these exampleadjustments may be performed programmatically by one or more suitablecomputer controllers.

Returning to the embodiment shown in FIG. 10 , showerhead 1006 andpedestal 1008 electrically communicate with RF power supply 1014 andmatching network 1016 for powering a plasma. In some embodiments, theplasma energy may be controlled by controlling one or more of a processstation pressure, a gas concentration, an RF source power, an RF sourcefrequency, and a plasma power pulse timing. For example, RF power supply1014 and matching network 1016 may be operated at any suitable power toform a plasma having a desired composition of radical species. Examplesof suitable powers are included above. Likewise, RF power supply 1014may provide RF power of any suitable frequency. In some embodiments, RFpower supply 1014 may be configured to control high- and low-frequencyRF power sources independently of one another. Example low-frequency RFfrequencies may include, but are not limited to, frequencies between 50kHz and 900 kHz. Example high-frequency RF frequencies may include, butare not limited to, frequencies between 1.8 MHz and 2.45 GHz. It will beappreciated that any suitable parameters may be modulated discretely orcontinuously to provide plasma energy for the surface reactions. In onenon-limiting example, the plasma power may be intermittently pulsed toreduce ion bombardment with the substrate surface relative tocontinuously powered plasmas.

In some embodiments, the plasma may be monitored in-situ by one or moreplasma monitors. In one scenario, plasma power may be monitored by oneor more voltage, current sensors (e.g., VI probes). In another scenario,plasma density and/or process gas concentration may be measured by oneor more optical emission spectroscopy sensors (OES). In someembodiments, one or more plasma parameters may be programmaticallyadjusted based on measurements from such in-situ plasma monitors. Forexample, an OES sensor may be used in a feedback loop for providingprogrammatic control of plasma power. It will be appreciated that, insome embodiments, other monitors may be used to monitor the plasma andother process characteristics. Such monitors may include, but are notlimited to, infrared (IR) monitors, acoustic monitors, and pressuretransducers.

In some embodiments, the plasma may be controlled via input/outputcontrol (IOC) sequencing instructions. In one example, the instructionsfor setting plasma conditions for a plasma process phase may be includedin a corresponding plasma activation recipe phase of a depositionprocess recipe. In some cases, process recipe phases may be sequentiallyarranged, so that all instructions for a deposition process phase areexecuted concurrently with that process phase. In some embodiments,instructions for setting one or more plasma parameters may be includedin a recipe phase preceding a plasma process phase. For example, a firstrecipe phase may include instructions for setting a flow rate of aninert and/or a reactant gas, instructions for setting a plasma generatorto a power set point, and time delay instructions for the first recipephase. A second, subsequent recipe phase may include instructions forenabling the plasma generator and time delay instructions for the secondrecipe phase. A third recipe phase may include instructions fordisabling the plasma generator and time delay instructions for the thirdrecipe phase. It will be appreciated that these recipe phases may befurther subdivided and/or iterated in any suitable way within the scopeof the present disclosure.

In some deposition processes, plasma strikes last on the order of a fewseconds or more in duration. In certain implementations, much shorterplasma strikes may be used. These may be on the order of 10 ms to 1second, typically, about 20 to 80 ms, with 50 ms being a specificexample. Such very short RF plasma strikes require extremely quickstabilization of the plasma. To accomplish this, the plasma generatormay be configured such that the impedance match is set preset to aparticular voltage, while the frequency is allowed to float.Conventionally, high-frequency plasmas are generated at an RF frequencyat about 13.56 MHz. In various embodiments disclosed herein, thefrequency is allowed to float to a value that is different from thisstandard value. By permitting the frequency to float while fixing theimpedance match to a predetermined voltage, the plasma can stabilizemuch more quickly, a result which may be important when using the veryshort plasma strikes associated with some types of deposition cycles.

In some embodiments, pedestal 1008 may be temperature controlled viaheater 1010. Further, in some embodiments, pressure control fordeposition process station 1000 may be provided by butterfly valve 1018.As shown in the embodiment of FIG. 10 , butterfly valve 1018 throttles avacuum provided by a downstream vacuum pump (not shown). However, insome embodiments, pressure control of process station 1000 may also beadjusted by varying a flow rate of one or more gases introduced toprocess station 1000.

FIG. 11 shows a schematic view of an embodiment of a multi-stationprocessing tool 1100 with an inbound load lock 1102 and an outbound loadlock 1104, either or both of which may comprise a remote plasma source.A robot 1106, at atmospheric pressure, is configured to move wafers froma cassette loaded through a pod 1108 into inbound load lock 1102 via anatmospheric port 1110. A wafer is placed by the robot 1106 on a pedestal1112 in the inbound load lock 1102, the atmospheric port 1110 is closed,and the load lock is pumped down. Where the inbound load lock 1102comprises a remote plasma source, the wafer may be exposed to a remoteplasma treatment in the load lock prior to being introduced into aprocessing chamber 1114. Further, the wafer also may be heated in theinbound load lock 1102 as well, for example, to remove moisture andadsorbed gases. Next, a chamber transport port 1116 to processingchamber 1114 is opened, and another robot (not shown) places the waferinto the reactor on a pedestal of a first station shown in the reactorfor processing. While the embodiment depicted in FIG. 11 includes loadlocks, it will be appreciated that, in some embodiments, direct entry ofa wafer into a process station may be provided.

The depicted processing chamber 1114 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 11 . Each stationhas a heated pedestal (shown at 1118 for station 1), and gas lineinlets. It will be appreciated that in some embodiments, each processstation may have different or multiple purposes. While the depictedprocessing chamber 1114 comprises four stations, it will be understoodthat a processing chamber according to the present disclosure may haveany suitable number of stations. For example, in some embodiments, aprocessing chamber may have five or more stations, while in otherembodiments a processing chamber may have three or fewer stations.

FIG. 11 also depicts an embodiment of a wafer handling system 1190 fortransferring wafers within processing chamber 1114. In some embodiments,wafer handling system 1190 may transfer wafers between various processstations and/or between a process station and a load lock. It will beappreciated that any suitable wafer handling system may be employed.Non-limiting examples include wafer carousels and wafer handling robots.FIG. 11 also depicts an embodiment of a system controller 1150 employedto control process conditions and hardware states of process tool 1100.System controller 1150 may include one or more memory devices 1156, oneor more mass storage devices 1154, and one or more processors 1152.Processor 1152 may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.

FIG. 12 is a block diagram of a processing system suitable forconducting thin film deposition processes in accordance with certainembodiments. The system 1200 includes a transfer module 1203. Thetransfer module 1203 provides a clean, pressurized environment tominimize risk of contamination of substrates being processed as they aremoved between various reactor modules. Mounted on the transfer module1203 are two multi-station reactors 1209 and 1210, each capable ofperforming atomic layer deposition (ALD) and/or chemical vapordeposition (CVD) according to certain embodiments. Reactors 1209 and1210 may include multiple stations 1211, 1213, 1215, and 1217 that maysequentially or non-sequentially perform operations in accordance withdisclosed embodiments. The stations may include a heated pedestal orsubstrate support, one or more gas inlets or showerhead or dispersionplate.

Also mounted on the transfer module 1203 may be one or more single ormulti-station modules 1207 capable of performing plasma or chemical(non-plasma) pre-cleans, or any other processes described in relation tothe disclosed methods. The module 1207 may in some cases be used forvarious treatments to, for example, prepare a substrate for a depositionprocess. The module 1207 may also be designed/configured to performvarious other processes such as etching or polishing. The system 1200also includes one or more wafer source modules 1201, where wafers arestored before and after processing. An atmospheric robot (not shown) inthe atmospheric transfer chamber 1219 may first remove wafers from thesource modules 1201 to loadlocks 1221. A wafer transfer device(generally a robot arm unit) in the transfer module 1203 moves thewafers from loadlocks 1221 to and among the modules mounted on thetransfer module 1203.

In various embodiments, a system controller 1229 is employed to controlprocess conditions during deposition as described herein.

It may be appreciated that a plurality of process stations may beincluded in a multi-station processing tool environment, such as shownin FIG. 13 , which depicts a schematic view of an embodiment of amulti-station processing tool. Processing apparatus 1300 employs anintegrated circuit fabrication chamber 1363 that includes multiplefabrication process stations, each of which may be used to performprocessing operations on a substrate held in a wafer holder, such as apedestal, at a particular process station. In the embodiment of FIG. 13, the integrated circuit fabrication chamber 1363 is shown having fourprocess stations 1351, 1352, 1353, and 1354. Other similar multi-stationprocessing apparatuses may have more or fewer process stations dependingon the implementation and, for example, a desired level of parallelwafer processing, size/space constraints, cost constraints, etc. Alsoshown in FIG. 13 is substrate handler robot 1375, which may operateunder the control of system controller 1390, configured to movesubstrates from a wafer cassette (not shown in FIG. 13 ) from loadingport 1380 and into integrated circuit fabrication chamber 1363, and ontoone of process stations 1351, 1352, 1353, and 1354.

FIG. 13 also depicts an embodiment of a system controller 1390 employedto control process conditions and hardware states of processingapparatus 1300. System controller 1390 may include one or more memorydevices, one or more mass storage devices, and one or more processors,as described herein.

RF subsystem 1395 may generate and convey RF power to integrated circuitfabrication chamber 1363 via radio frequency input ports 1367. Inparticular embodiments, integrated circuit fabrication chamber 1363 maycomprise input ports in addition to radio frequency input ports 1367(additional input ports not shown in FIG. 13 ). Accordingly, integratedcircuit fabrication chamber 1363 may utilize 8 RF input ports. Inparticular embodiments, process stations 1351-1354 of integrated circuitfabrication chamber 165 may each utilize first and second input ports inwhich a first input port may convey a signal having a first frequencyand in which a second input port may convey a signal having a secondfrequency. Use of dual frequencies may bring about enhanced plasmacharacteristics.

As described above, one or more process stations may be included in amulti-station processing tool. FIG. 14 shows a schematic view of anembodiment of a multi-station processing tool 1400 with an inbound loadlock 1402 and an outbound load lock 1404, either or both of which maycomprise a remote plasma source. A robot 1406, at atmospheric pressure,is configured to move substrates or wafers from a cassette loadedthrough a pod 1408 into inbound load lock 1402 via an atmospheric port1410. A substrate is placed by the robot 1406 on a pedestal 1412 in theinbound load lock 1402, the atmospheric port 1410 is closed, and theload lock is pumped down. Where the inbound load lock 1402 comprises aremote plasma source, the substrate may be exposed to a remote plasmatreatment in the load lock prior to being introduced into a processingchamber 1414. Further, the substrate also may be heated in the inboundload lock 1402 as well, for example, to remove moisture and adsorbedgases. Next, a chamber transport port 1416 to processing chamber 1414 isopened, and another robot (not shown) places the substrate into thereactor on a pedestal of a first station shown in the reactor forprocessing. While the embodiment depicted in FIG. 14 includes loadlocks, it will be appreciated that, in some embodiments, direct entry ofa substrate into a process station may be provided. In variousembodiments, the soak gas is introduced to the station when thesubstrate is placed by the robot 1406 on the pedestal 1412.

The depicted processing chamber 1414 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 14 . Each stationhas a heated pedestal (shown at 1418 for station 1), and gas lineinlets. It will be appreciated that in some embodiments, each processstation may have different or multiple purposes. For example, in someembodiments, a process station may be switchable between an ALD andPEALD process mode. Additionally or alternatively, in some embodiments,processing chamber 1414 may include one or more matched pairs of ALD andplasma-enhanced ALD process stations. While the depicted processingchamber 1414 includes four stations, it will be understood that aprocessing chamber according to the present disclosure may have anysuitable number of stations. For example, in some embodiments, aprocessing chamber may have five or more stations, while in otherembodiments a processing chamber may have three or fewer stations.

FIG. 14 depicts an embodiment of a wafer handling system 1490 fortransferring substrates within processing chamber 1414. In someembodiments, wafer handling system 1490 may transfer substrates betweenvarious process stations and/or between a process station and a loadlock. It will be appreciated that any suitable wafer handling system maybe employed. Non-limiting examples include wafer carousels and waferhandling robots. FIG. 14 also depicts an embodiment of a systemcontroller 1450 employed to control process conditions and hardwarestates of process tool 1400. System controller 1450 may include one ormore memory devices 1456, one or more mass storage devices 1454, and oneor more processors 1452. Processor 1452 may include a CPU or computer,analog and/or digital input/output connections, stepper motor controllerboards, etc. In some embodiments, system controller 1450 includesmachine-readable instructions for performing operations such as thosedescribed herein.

In some embodiments, system controller 1450 controls the activities ofprocess tool 1400. System controller 1450 executes system controlsoftware 1458 stored in mass storage device 1454, loaded into memorydevice 1456, and executed on processor 1452. Alternatively, the controllogic may be hard coded in the system controller 1450. ApplicationsSpecific Integrated Circuits, Programmable Logic Devices (e.g.,field-programmable gate arrays, or FPGAs) and the like may be used forthese purposes. In the following discussion, wherever “software” or“code” is used, functionally comparable hard coded logic may be used inits place. System control software 1458 may include instructions forcontrolling the timing, mixture of gases, amount of gas flow, chamberand/or station pressure, chamber and/or station temperature, substratetemperature, target power levels, RF power levels, substrate pedestal,chuck and/or susceptor position, and other parameters of a particularprocess performed by process tool 1400. System control software 1458 maybe configured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components used to carry out variousprocess tool processes. System control software 1458 may be coded in anysuitable computer readable programming language.

While the subject matter disclosed herein has been particularlydescribed with respect to the illustrated embodiments, it will beappreciated that various alterations, modifications and adaptations maybe made based on the present disclosure, and are intended to be withinthe scope of the present invention. It is to be understood that thedescription is not limited to the disclosed embodiments but, on thecontrary, is intended to cover various modifications and equivalentarrangements included within the scope of the claims.

What is claimed is:
 1. A method, comprising: providing a substrate to aprocessing chamber, the substrate having a first material adjacent toand covering a surface of a second material; modifying a layer of thefirst material by flowing a first process gas onto the substrate andthereby creating a modified layer of the first material; removing themodified layer of the first material by flowing a second process gasonto the substrate; and converting, when the surface of the secondmaterial is uncovered via removal of the modified layer, the surface toa converted layer of the second material by flowing a third process gasonto the substrate, wherein the first and second process gases are lessreactive with the converted layer than with the first material and thesecond material.
 2. The method of claim 1, further comprising:modifying, after the converting, the converted layer to a modifiedconverted layer of material by flowing a fourth process gas onto thesubstrate; and removing the modified converted layer by flowing a fifthprocess gas onto the substrate.
 3. The method of claim 1, whereinflowing the third process gas occurs before the modifying.
 4. The methodof claim 1, wherein flowing the third process gas occurs after themodifying.
 5. The method of claim 4, wherein flowing the third processgas occurs before the removing.
 6. The method of claim 5, furthercomprising flowing a purge gas after flowing the third process gas andbefore the removing.
 7. The method of claim 4, wherein flowing the thirdprocess gas occurs after the removing.
 8. The method of claim 1, whereinflowing the third process gas onto the substrate at least partiallyoverlaps with flowing the first process gas onto the substrate.
 9. Themethod of claim 1, wherein flowing the third process gas onto thesubstrate at least partially overlaps with flowing the second processgas onto the substrate.
 10. The method of claim 1, wherein flowing thethird process gas onto the substrate at least partially overlaps withflowing the first process gas onto the substrate and with flowing thesecond process gas onto the substrate.
 11. The method of claim 1,wherein the converting occurs when the surface of the second material isuncovered during or after the removing of the first material.
 12. Themethod of claim 1, wherein: during the removing, the second process gasremoves the modified layer of the first material at a first etch rate,and during the removing, the second process gas removes the convertedlayer at a second etch rate that is about equal to or less than 50% ofthe first etch rate.
 13. The method of claim 12, wherein the second etchrate is about equal to or less than 15% of the first etch rate.
 14. Themethod of claim 12, wherein during the removing, the second process gasis capable of removing the second material at a third etch rate higherthan the first etch rate.
 15. The method of claim 1, wherein: the firstprocess gas comprises modifying molecules, the second process gascomprises removal molecules, and the third process gas comprisesconverting molecules.
 16. The method of claim 1, wherein the thirdprocess gas comprises a precursor.
 17. The method of claim 1, whereinthe converted layer is a monoatomic layer of the second material. 18.The method of claim 1, wherein the first material and the secondmaterial are oxides.
 19. The method of claim 1, wherein the firstmaterial and/or the second material are semiconductor oxides.
 20. Themethod of claim 1, wherein the converted layer is passive to the secondprocess gas.
 21. The method of claim 1, wherein a reaction between theconverted layer and the second process gas does not produce byproducts.22. The method of claim 1, further comprising: repeating the modifyingand the removing to remove an amount the first material before theconverting.
 23. The method of claim 1, wherein: the first materialcomprises an aluminum oxide, the second material comprises a zinc oxide,the first process gas comprises a hydrogen fluoride, the second processgas comprises trimethylaluminum, the third process gas compriseszirconium tetrachloride, and the converted layer comprises a zirconiumoxide.
 24. The method of claim 1, further comprising: removing theconverted layer by flowing a fourth process gas onto the substrate,wherein the fourth process gas comprises dimethylaluminum chloride. 25.The method of claim 1, wherein the converting comprises a cationexchange between an element in the third process gas and the secondmaterial.
 26. The method of claim 1, wherein the modifying and theremoving occur while the substrate is maintained at the same, orsubstantially the same, temperature.
 27. The method of claim 1, wherein:the modifying occurs while the substrate is maintained at a firsttemperature, and the removing occurs while the substrate is maintainedat a second temperature different than the first temperature.
 28. Themethod of claim 1, wherein during the converting, water vapor is notprovided to the substrate.
 29. A method, comprising: providing asubstrate to a processing chamber, the substrate having a first materialadjacent to and covering a surface of a second material; modifying alayer of the first material by flowing a first process gas onto thesubstrate and thereby creating a modified layer of the first material;removing the modified layer of the first material by flowing a secondprocess gas onto the substrate; and selectively converting, when thesurface of the second material is uncovered via removal of the modifiedlayer, the surface of the second material to a layer of etch stopmaterial, wherein the layer of etch stop material is only positioned ontop of the second material, such that during the removing, the modifiedlayer of the first material and the layer of etch stop material areexposed to the second process gas and the second process gas is lessreactive with the layer of etch stop material than with the modifiedlayer of the first material and the second material.
 30. An apparatusfor semiconductor processing, the apparatus comprising: a processingchamber that includes an interior and a substrate support configured tosupport a substrate in the interior; a process gas unit configured toflow a first process gas comprising a modifying molecule onto thesubstrate in the processing chamber, a second process gas comprising aremoval molecule onto the substrate in the processing chamber, and athird process gas comprising a conversion molecule onto the substrate inthe processing chamber; and a controller with instructions that areconfigured to: cause the first process gas to flow onto the substrateand thereby create a modified layer of a first material on thesubstrate, wherein the substrate has the first material adjacent to andcovering a surface of a second material, cause the second process gas toflow onto the substrate and thereby remove the modified layer of thefirst material, and cause the third process gas to flow onto thesubstrate to convert, when the surface of the second material isuncovered, the surface to a converted layer of the second material,wherein the first and second process gases are less reactive with theconverted layer than with the first material and the second material.